Chapter IX: Appendix: “Rhizopods in Poliomyelitis acuta.” (3)

_T. brucei_ is rapidly fatal to the small laboratory animals, such as rats and mice. Horses, asses and dogs practically always succumb to its attacks, while a very small number of cattle recover from “nagana.” The disease is characterized by fever, destruction of red blood corpuscles, severe emaciation and by an infiltration of coagulated lymph in the subcutaneous tissue of the neck, abdomen and extremities giving a swollen appearance thereto. The natural reservoirs in which _T. brucei_ has been long acclimatized are unaffected by the trypanosomes, while the newer hosts, such as imported cattle in Africa, are rapidly destroyed by their action.

The general morphology and life history in the vertebrate host is that of a typical trypanosome (fig. 40). Its length is from 12 µ to 35 µ, its breadth from 1·5 µ to 4 µ. Multiplication by longitudinal division proceeds in the peripheral blood (fig. 26), while latent, leishmaniform bodies are produced in the internal organs.

Bruce and colleagues[99] have quite recently (June, 1914) described the development of a Zululand strain of _T. brucei_ in _G. morsitans_. The tsetse flies were bred out in Nyasaland. In vertebrate blood the _brucei_ strain was polymorphic. The development was like that found for _T. gambiense_ in _G. palpalis_ (fig. 30), and by Bruce and colleagues for _T. rhodesiense_ in _G. morsitans_ in Nyasaland. Long trypanosomes were found in the proventriculus of the tsetse. Crithidial, rounded or encysted, and immature “blood forms” occurred in the salivary glands; and finally infective, stumpy, “blood forms” were differentiated in the salivary glands. The period of development of _T. brucei_ in _G. morsitans_ takes about three weeks, and then the fly becomes infective. Bruce believes that _T. rhodesiense_ of Nyasaland and _T. brucei_ of Zululand are the same, their cycles of development in _G. morsitans_ being “marvellously alike.” (But see Laveran, p. 80.)

[99] _Proc. Roy. Soc._, B, lxxxvii, p. 526.

_T. brucei_ has been cultivated with difficulty by Novy and MacNeal, using blood agar. The best treatment for nagana is arsenic in some form.

It is probable that more than one trypanosome has been confused under the name _T. brucei_, more especially as the occurrence of many species of trypanosomes in various animals in Africa was not suspected until comparatively recent times. It has been shown by Stephens and Blacklock (1913) that the original Zululand strain of _T. brucei_ was monomorphic, while the organism sent from Uganda, and at the time believed by Bruce to be the same as the Zululand trypanosome, has been found to be polymorphic, with morphological resemblances to _T. rhodesiense_. Stephens and Blacklock[100] have suggested the name _T. ugandæ_ for the polymorphic trypanosome, which, however, has marked resemblances with *Trypanosoma pecaudi*, and they are, perhaps, identical. _T. pecaudi_ was the name given by Laveran[101] in 1907 to the causal agent of “baleri” in equines and sheep in the French Sudan. _T. pecaudi_, which is dimorphic, is widely distributed in Africa. An extremely small number of both _T. pecaudi_ and _T. ugandæ_ have been shown to possess posterior nuclei. _T. pecaudi_ is transmitted by various species of _Glossina_, and is said to develop in the gut and proboscis of the fly.

[100] _Proc. Roy. Soc._, B, lxxxvi, p. 187.

[101] _C.R. Acad. Sci._, cxliv, p. 243.

On the other hand, Bruce and colleagues (1914), examining a strain sent from Zululand in 1913, state that _T. brucei_ is polymorphic. Bruce (1914) suggests that passage through laboratory hosts has influenced and altered the morphology of the parasite.

*Trypanosoma evansi*, Steel, 1885.

Syn.: _Spirochæta evansi_, Steel, 1885; _Hæmatomonas evansi_,
Crookshank, 1886; _Trichomonas evansi_, Crookshank, 1886.

_Trypanosoma evansi_, first found by Evans in 1880, in India, is the causal agent of the disease known as “surra.” The malady affects more particularly horses, mules, camels and cattle in India and neighbouring countries, such as Burma and Indo-China. It occurs also in Java, the Philippines, Mauritius and North Africa. Elephants may be affected. A serious outbreak among cattle in Mauritius occurred in 1902, the disease being imported into the island. The symptoms are fever, emaciation, œdema, great muscular weakness and paralysis culminating in death.

_T. evansi_ varies from 18 µ to 34 µ in length and 1·5 µ to 2 µ in breadth. It has a pointed posterior extremity, and, anteriorly, there is a free portion to the flagellum (fig. 41). It is possibly monomorphic, but a few broad forms occur. The trypanosome multiplies by longitudinal fission in the blood. Rounded leishmaniform stages occur in the spleen of the vertebrate host, which stages Walker[102] (1912) considers to be phases of schizogony.

[102] _Philippine Journ. Sc._ (Sect. B), vii, p. 53.

The parasite is transmitted in nature by various species of _Tabanus_ and _Stomoxys_, though at present little is known of the life-history within these invertebrate hosts.

Dogs are said to contract the disease by feeding on animals dead of surra.

A variety of _T. evansi_ is the cause of “mbori” in dromedaries in Africa (Sahara and Sudan). Another possible variety, or closely allied form, is _T. soudanense_, the causal agent of “el debab” in camels and horses in North Africa, especially Algeria and Egypt.

An extraordinary example of the possible infection of a human being with an animal trypanosome is recorded in the case of Professor Lanfranchi, of the Veterinary School, Parma. The Professor became infected with trypanosomes, although only nagana and surra were maintained in his laboratory, and he himself had never visited the tropics. He suffered from irregular attacks of fever and was œdematous, but his mind remained clear. The identification of the trypanosome from Lanfranchi’s blood has been a matter of great difficulty. Apparently Mesnil and Blanchard (1914)[103] consider the strain found in the patient is almost indistinguishable in its reactions from _T. gambiense_, though the parasite is monomorphic. Lanfranchi considers that he was infected with _T. evansi_.

[103] _Bull. Soc. Path. Exot._, vii, p. 196.

*Trypanosoma equinum*, Voges, 1901.

Syn.: _Trypanosoma elmassiani_, Lignières.

_Trypanosoma equinum_ was found by Elmassian to be the cause of the fatal disease, “mal de caderas,” of horses and dogs, in South America (Paraguay, Argentine, Bolivia). The name refers to the fact that in the disease, as in other trypanosomiases, the hind quarters become paralysed. Cattle are refractory to inoculation.

_T. equinum_ is about 22 µ to 24 µ long and about 1·5 µ broad (fig. 42). Although this trypanosome is very active, yet it is characterized by the blepharoplast (kinetic nucleus) being very minute or even absent, as the granule sometimes seen may be the basal granule of the flagellum.

The mode of transmission of _T. equinum_ is not known with absolute certainty. Migone has shown that the parasite causes a fatal disease in the large South American rodent, the capybara (_Hydrochœrus capybara_). This animal appears to be a reservoir of the parasite. Dogs may become infected by eating diseased capybaras, and it is suggested that the infection is spread from the dogs to horses by the agency of fleas. Some authorities consider that _T. equinum_ may be spread by various _Tabanidæ_ and by _Stomoxys_. Neiva (1913)[104] doubts all these modes of transmission in Brazil, and suggests _Chrysops_ or _Triatoma_ as vectors.

[104] _Brazil Medico_, xxvii, p. 366.

*Trypanosoma equiperdum*, Doflein, 1901.

Syn.: _Trypanosoma rougeti_, Laveran and Mesnil.

The malady of horses known as “dourine” or “mal du coït” is due to a trypanosome, _T. equiperdum_, discovered by Rouget in 1894. “Dourine”--also known as “stallion disease” or “covering disease”--is found among horses and asses in Europe, India, North Africa and North America. The trypanosome is transmitted by coitus, and so far as is known not by insect agency.

The progress of the disease may be considered under three periods. The _period of œdema_, when signs of œdema of the genitalia are seen. The œdema is generally painless and non-inflammatory. This period lasts about a month. It is succeeded by the _period of eruption_, which sets in about two months after infection. Circular œdematous areas (“plaques”), often about the size of a two-shilling piece, appear under the skin of the sides and hind quarters, and also, at times, under the skin of the neck, thighs and shoulders. The eruption is variable, but usually lasts about a week and leaves the animal in an enfeebled condition. Gland enlargement and swelling of the joints and synovia also may occur. The third period of the disease is described as that _of anæmia and paralysis_. The animal becomes very anæmic, emaciation is marked, superficial non-healing abscesses often form, and conjunctivitis and ulcerative keratitis can occur. Paralysis ensues, and in from two to eighteen months the animal dies. In the acute form of the disease the animal may die after the first period from acute paralysis.

It is difficult to find the trypanosomes in naturally infected animals, and they are best obtained from the plaques of the eruption. Apparently the parasite occurs more in the lymph than in the blood.

Ruminants are said to be refractory to this trypanosome.

_T. equiperdum_ is about 25 µ to 28 µ in length on an average, but varies from 16 µ to 35 µ. Its cytoplasm is relatively clear, and does not show chromatic granules (fig. 43). It is stated to be monomorphic.

It has been shown recently by Blacklock and Yorke (1913)[105] that there is another trypanosome giving rise to dourine in horses. This trypanosome is dimorphic (resembling _T. pecaudi_ and _T. ugandæ_), and is named _T. equi_. Previously _T. equiperdum_ and _T. equi_ had been confused.

[105] _Proc. Roy. Soc._, B, lxxxvii, p. 89.

Uhlenhuth, Hübner and Worthe have demonstrated the presence of endotoxins in _T. equiperdum_. These endotoxins may be set free by trypanolysis.

*Trypanosoma theileri*, Bruce, 1902.

This parasite, 60 µ to 70 µ long, and 4 µ to 5 µ broad, is distinguished for its large size, though it is not so large as _T. ingens_ from Uganda oxen, whose length may be 72 µ to 122 µ, and breadth 7 µ to 10 µ. The posterior end of _T. theileri_ is drawn out. Small forms of the flagellate are known, 25 µ to 53 µ in length. Probably other forms of the parasite have the nucleus posterior, and these flagellates were formerly separated as _T. transvaaliense_ (Laveran, 1902). Myoneme fibrils may be seen on its body. The pathogenicity of this organism is doubtful, it was formerly thought to be the causal agent of “gall-sickness” in cattle in South Africa. _T. theileri_ also occurs in Togoland, German East Africa, and Transcaucasia. Allied or identical parasites occur in cattle in India.

_Trypanosoma theileri_, specific to cattle, is perhaps transmitted by the fly _Hippobosca rufipes_ in South Africa.

*Trypanosoma hippicum*, Darling, 1910.

_Trypanosoma hippicum_ causes the disease of mules known as “murrina.”[106] It was found in mules imported to Panama from the United States. It can live in other equines. The parasite varies from 18 µ to 28 µ in length, and is from 1·5 µ to 3 µ broad. Its undulating membrane is little folded. The trypanosome has a noticeable blepharoplast. It can penetrate mucous membranes, and it is thought that the trypanosome may be transmitted during coitus. It may also be spread mechanically by species of _Musca_, _Sarcophaga_ and _Compsomyia_, sucking the wounds of infected animals and carrying over the trypanosomes to wounds on healthy ones.

[106] _Bull. Soc. Path. Exot._, iii, p. 381.

*Endotrypanum schaudinni*, Mesnil and Brimont, 1908.

This organism was discovered in the blood of a sloth (_Cholœpus didactylus_), in South America (French Guiana).[107] It possesses special interest, in that the best known form of the organism is endoglobular, inhabiting the erythrocytes of the sloth. A free trypanosome in the same animal was considered to be different from the endoglobular form, which was somewhat like a peg-top, and possessed a short flagellum. Darling[108] (November, 1914) has seen the organism in Panama. He describes free crithidial forms in shed blood, but not in the blood-stream of the sloth.

[107] _C. R. Soc. Biol._, lxv, p. 581.

[108] _Journ. Med. Research_, xxxi, p. 195.

*Trypanosoma boylei*, Lafont, 1912.

This is a parasite of the Reduviid bug, _Conorhinus rubrofasciatus_. The insect attacks man in Mauritius, Réunion and other places. Lafont infected rats and mice by intraperitoneal injection with the gut-contents of infected bugs. Trypanosomes appeared in the mice. Other flagellate types were assumed by the parasites in the bug.

MONOMORPHIC TRYPANOSOMES.

A number of trypanosomes, characterized by relative uniformity in size and structure, may be considered under this heading. They occur in cattle, sheep, goats and horses in Africa, especially West Africa. Morphologically, they are characterized by the posterior (aflagellar) part of the body being swollen, while the anterior part narrows. The nucleus is central and situated at the commencement of the narrowing of the body. The blepharoplast is almost terminal, the undulating membrane is narrow and not markedly folded, so that the flagellar border lies close to or along the body. The flagellum may or may not possess a free portion.

Some recent workers have considered that _T. brucei_ (Zululand strain) and _T. evansi_ are also monomorphic, but they do not exhibit the general characteristics outlined above. _T. brucei_ and _T. evansi_ have already been considered separately.

The monomorphic trypanosomes, as defined above, include:--

*Trypanosoma vivax*, Ziemann, 1905.

This trypanosome[109] occurs in cattle, sheep and goats, and was first found in the Cameroons. It is fatal to cattle. Equines are also affected. Antelopes are the possible reservoirs of the trypanosome. It is probably transmitted by _Glossina palpalis_ and other tsetse flies. Its movement is very active. It possesses a free flagellum (fig. 45) and it averages 23 µ to 24 µ in length. _T. cazalboui_ (Laveran, 1906)--the causal agent of “souma” in bovines and equines in the French Sudan--is probably synonymous with _T. vivax_.

[109] See Bruce and colleagues (1910), _Proc. Roy. Soc._, B, lxxxiii, p. 15.

*Trypanosoma capræ* (Kleine, 1910) is allied, but is somewhat broader and more massive. It was found in goats in Tanganyika.

*Trypanosoma congolense*, Broden, 1904.

Probable synonyms.--_Trypanosoma dimorphon_, Laveran and Mesnil,
1904; _Trypanosoma nanum_, Laveran, 1905; _Trypanosoma pecorum_,
Bruce, 1910; _Trypanosoma confusum_, Montgomery, 1909.

This trypanosome causes disease among horses (_e.g._, Gambia horse sickness), cattle, sheep, goats, pigs, and dogs. It is widely distributed in Central Africa (_e.g._, Gambia, Congo, Uganda, Nyasaland), the strain probably being maintained naturally in big game. It is transmitted by various _Glossinæ_, and perhaps by _Tabanus_ and _Stomoxys_. It is said to develop in the gut and proboscis of _Glossina palpalis_ and _G. morsitans_. The trypanosome averages 13 µ to 14 µ in length and has no free flagellum (fig. 46). It is about 2 µ broad. Formerly _T. nanum_ and _T. pecorum_ were said to differ in their pathogenicity, the former being said not to infect the smaller laboratory animals. Yorke and Blacklock (1913), however, consider that the virulence varies and that these trypanosomes are probably the same.

The _T. dimorphon_ originally obtained by Dutton and Todd (1903) in Gambian horse sickness has been shown to be a mixture of _T. vivax_ and _T. congolense_.

*Trypanosoma simiae* (_T. ignotum_) is like _T. congolense_. It averages 17·5 µ long. It is virulent to monkeys and pigs.

*Trypanosoma uniforme*, Bruce, 1910.

This trypanosome was found in oxen in Uganda.[110] It can be inoculated to oxen, goats and sheep, but is refractory to dogs, rats and guinea-pigs. It has been found in antelopes. It resembles _T. vivax_, but is smaller (fig. 47), averaging 16 µ in length. A free flagellum is present. It is transmitted by _Glossinæ_.

[110] _Proc. Roy. Soc._, B, lxxxiii, p. 176.

Many other trypanosomes occur in mammals, while birds, reptiles, amphibia (fig. 48) and fish also harbour them. The discussion of these forms does not come within the scope of the present work. They are dealt with in Laveran and Mesnil’s “Trypanosomes et Trypanosomiases,” 2nd edit., 1912.

GENERAL NOTE ON DEVELOPMENT OF TRYPANOSOMES IN GLOSSINA.

Before concluding the account of trypanosomes, it may be of interest to remark that several African trypanosomes develop in various species of _Glossina_, and are found in different parts of the alimentary tract and in the proboscis. Thus (_a_) _T. vivax_, _T. uniforme_ and _T. capræ_ develop in the fly’s proboscis (labial cavity and hypopharynx) only; (_b_) _T. congolense_, _T. simiæ_ and _T. pecaudi_ develop first in the gut of the fly and then pass forward to its proboscis; and (_c_) _T. gambiense_ and _T. rhodesiense_ develop first in the gut and later invade the salivary glands of the tsetse. The proboscis or the salivary glands in such cases are termed by Duke[111] the _anterior station_ of the trypanosome, wherein it completes its development.

[111] _Repts. Sleeping Sickness Commission Roy. Soc._ (1913), xiii, p. 82.

ADAPTATION OF TRYPANOSOMES.

These flagellates may exhibit power of adaptation to changes of environment, such as those due to the administration of drugs, change of host, etc. A few examples of such mutations may be briefly considered:--

(1) _Blepharoplastless Trypanosomes_.--_T. brucei_ may become resistant to pyronin and oxazine. Accompanying this drug resistance is a change in morphology, namely, the loss of the blepharoplast (Werbitzki).[112] A race or strain of blepharoplastless trypanosomes may be thus produced which retains its characteristic feature after as many as 130 passages (Laveran).[113] Oxazine is the more powerful drug, and it acts directly on the blepharoplast. (Compare the natural blepharoplastless character of _T. equinum_.)

[112] _Centralbl. f. Bakt._ (1910), Orig., liii, p. 303.

[113] _Bull. Soc. Path. Exot._, iv, p. 233.

(2) Reference has been made on p. 93 to the experiments of Gonder, who showed that a strain of _T. lewisi_ rendered resistant to arsenophenylglycin lost its resistance after passage through the rat louse. This is in marked contrast with the retention of drug resistance during passage by inoculation from rat to rat.

(3) _T. lewisi_ from the blood of a rat when transferred to a snake seems largely to disappear, as very few flagellates are seen. When blood from the snake is inoculated into a clean rat, then trypanosomes reappear in the rat, but they are not all like those originally inoculated. It seems certain that, in such a case, changes in form and virulence of the trypanosome have occurred. Similar experiments were made with _T. brucei_ from rats to adders and other animals and back to rats. Changes in the form and virulence of _T. brucei_ occurred.

These interesting experiments were performed by Wendelstadt and Fellmer.[114]

[114] _Zeitschr. f. Immunitatsforschung_, iv, p. 422 (1909), and v, p. 337 (1910).

Genus. *Herpetomonas*, Saville Kent, 1881.

_Herpetomonas_ is a generic name for certain flagellates possessing a vermiform or snake-like body, a nucleus placed approximately centrally, and a blepharoplast (kinetic nucleus) near the flagellar end. There is no undulating membrane (fig. 49, _a_). The organisms included in this genus certainly possess one flagellum, while according to Prowazek (1904) _Herpetomonas muscæ-domesticæ_, the type species, possesses two flagella united by a membrane. Patton,[115] Porter[116] and others affirm, however, that the biflagellate character of _H. muscæ-domesticæ_ (from the gut of the house-fly) is merely due to precocious division. The matter is further complicated by the generic name _Leptomonas_, given by Kent in 1881, to an uniflagellate organism found by Bütschli in the intestine of the Nematode worm, _Trilobus gracilis_. This parasite, _Leptomonas bütschlii_, has not yet been completely studied. Until these controversial points relating to the identity or separation of _Herpetomonas_ and _Leptomonas_ have been satisfactorily settled, we may retain the better known name _Herpetomonas_ for such uniflagellate, vermiform organisms. However, the name _Leptomonas_, having been used by Kent two pages earlier in his book (“Manual of the Infusoria”) than _Herpetomonas_, would have priority if the two generic names were ultimately shown to be synonymous.

[115] _Arch. f. Protist._, xiii, p. 1.

[116] _Parasitology_, ii, p. 367.

A full discussion of these interesting and important flagellates hardly comes within the purview of the present work; brief mention can only be given here to certain species.

The Herpetomonads occur principally in the digestive tracts of insects, such as Diptera and Hemiptera. They are also known in the guts of fleas and lice, but are not confined to blood-sucking insects. One example, _H. ctenocephali_ (Fantham, 1912)[117] occurs in the digestive tracts of dog fleas, _Ctenocephalus canis_, in England, France, Germany, Italy, India, Tunis, etc. It is a natural flagellate of the flea, and might easily be confused with stages of blood parasites in the gut of the dog flea. Dog fleas are stated by Basile to transmit canine kala-azar, which is believed to be the same as human infantile kala-azar. Confusion is further likely to arise since herpetomonads pass through pre-flagellate, flagellate and post-flagellate or encysted stages; pre- and post-flagellate stages being oval or rounded and _Leishmania_-like. The post-flagellate stages are shed in the fæces, and are the cross-infective stages by means of which new hosts are infected by the mouth. The possible presence of such natural flagellates must always be considered when experimenting with fleas, lice, mosquitoes, etc., as possible vectors of pathogenic flagellates like _Leishmania_ and _Trypanosoma_. _H. pediculi_ (Fantham, 1912) occurs in human body lice.[118] See further remarks on pp. 107, 112.

[117] _Bull. Path. Exot._, vi, p. 254.

[118] _Proc. Roy. Soc._, B, lxxxiv, p. 505.

Laveran and Franchini (1913–14)[119] have recently succeeded in inoculating _Herpetomonas ctenocephali_, from the gut of the dog flea, intraperitoneally into white mice, and producing an experimental leishmaniasis in the mice. A dog was also infected. They have also succeeded in infecting mice with _H. pattoni_--a natural flagellate of the rat flea--by mixing infected rat fleas with the food of the mice, and by causing them to ingest infected fæces of rat fleas. Further, they have shown that infection with the herpetomonas occurs naturally by this method, that is, by the rodents eating the fleas and not by the insects inoculating the flagellates into the vertebrates when sucking blood. These experiments shed an interesting light on the probable origin of _Leishmania_ and its cultural herpetomonad stage, which were very probably once parasitic flagellates in the gut of an insect.

[119] _C. R. Acad. Sci._, clvii, pp. 423, 744. _Ibid._, clviii, pp. 450, 770. _Bull. Soc. Path. Exot._, vii, 605.

Fantham and Porter[120] (1914–15) have shown that young mice may be inoculated or fed with _Herpetomonas jaculum_, from the gut of the Hemipteran, _Nepa cinerea_ (the so-called “water-scorpion”), with fatal results. The pathogenic effects are like those of kala-azar. They also showed that the post-flagellate stages of the herpetomonads seemed most capable of developing in the vertebrate.

[120] _Proc. Camb. Philosoph. Soc._, xviii, p. 39.

A herpetomonad, _H. davidi_, has been found in the latex of species
of the plant-genus _Euphorbia_ in Mauritius, India, Portugal, etc. It
is apparently transmitted to the plants by _Hemiptera_. The plants
sometimes suffer from “flagellosis.”

Franchini (1913)[121] has described a new parasite, _Hæmocystozoon brasiliense_, from the blood of a man who had lived in Brazil for many years. It possesses flagellate and rounded stages, and is closely allied to the herpetomonads.

[121] _Bull. Soc. Path. Exot._, vi, pp. 156, 333, 377.

Genus. *Crithidia*, Léger, 1902, emend. Patton, 1908.

_Crithidia_ is the generic name of vermiform flagellates with a central nucleus, a blepharoplast or kinetic nucleus in the neighbourhood of the principal nucleus, and a rudimentary undulating membrane bordered by a flagellum arising from a basal granule, which is the centrosome of the kinetic nucleus (fig. 49_b_). The anterior or flagellar end of the body is attenuated and fades off as the undulating membrane.

_Crithidia fasciculata_, the type species, was found by Léger in the alimentary canal of _Anopheles maculipennis_. Crithidia occur in bugs, flies, fleas,[122] and ticks. Some of them are found in the body-fluid of the invertebrate host as well as in the gut. Others may be restricted to the body cavity or intestine respectively. _C. melophagia_ from the sheep-ked, _Melophagus ovinus_, and _C. hyalommæ_ from the hæmocœlic fluid of the tick, _Hyalomma ægyptium_, pass into the ovaries and eggs of their hosts, and the young keds or ticks are born infected.

[122] See Porter, _Parasitology_, iv, p. 237.

_C. fasciculata_ has been shown by Laveran and Franchini to be inoculable into white mice, producing a sort of experimental leishmaniasis therein. In one case cutaneous lesions were produced like those of Oriental sore.

Crithidia are natural flagellates of Arthropoda, with their own pre-flagellate, flagellate and post-flagellate stages, and must not be confused with transitory crithidial stages of trypanosomes.

Genus. *Leishmania*, Ross, 1903.

With an oval body containing nucleus and blepharoplast (kinetic nucleus) but no flagellum. An intracellular parasite in the vertebrate host.

Included in the genus _Leishmania_ are three species, namely:--

(1) _Leishmania donovani_, Laveran and Mesnil, 1903, the parasite
of Indian kala-azar, a generalized systemic disease, usually
fatal, occurring in subjects of all ages.
(2) _Leishmania tropica_, Wright, 1903, the parasite of Delhi boil,
Oriental sore, Aleppo button--a localized, cutaneous disease,
usually benign.
(3) _Leishmania infantum_, Nicolle, 1908, the parasite of infantile
kala-azar, occurring in children (and a few adults) around
the shores of the Mediterranean. The disease is perhaps a
form of Indian kala-azar, and the parasite is probably identical
with _L. donovani_.

These diseases may be termed collectively leishmaniases. The morphology of the various species is practically identical.

*Leishmania donovani*, Laveran and Mesnil, 1903.

Syn.: _Piroplasma donovani_, Laveran and Mesnil.

The parasite of Indian kala-azar was demonstrated in 1900 by Leishman from a _post-mortem_ examination of a case of “Dum-Dum fever,” but details were not published till May, 1903. In July, 1903, Donovan found similar bodies from cases in Madras. Rogers succeeded in cultivating the parasite in July, 1904.[123] The original centre of the disease was probably Assam; it occurs also in Madras, Ceylon, Burma, Indo-China, China and Syria. A variety of this leishmaniasis is found in the Sudan. The patient becomes emaciated, with a greatly enlarged spleen. There is anæmia and leucopenia.

[123] The literature up to 1912, on kala-azar and other leishmaniases is reviewed in the _Kala-azar Bulletin_. Afterwards in the _Tropical Diseases Bulletin_.

The parasite, commonly known as the Leishman-Donovan body, is intracellular (fig. 50, 2, 3). It is found in the endothelial cells of the capillaries of the liver, spleen, bone-marrow, lymphatic glands and intestinal mucosa, and in the macrophages of the spleen and bone-marrow. Some host cells may contain many parasites. It is rather rare in the circulating blood, but may be found in the blood from the femoral, portal and hepatic veins. It does not occur in the red blood corpuscles as was formerly thought. The parasites liberated from the endothelial cells are taken up by the mononuclear and polymorphonuclear leucocytes. The Leishman-Donovan body is the resting stage of a flagellate. As found in man it is a small, oval organism, about 2·5 µ to 3·5 µ in length by 2 µ in breadth, and containing two chromatinic bodies, corresponding to the nucleus and kinetic nucleus (blepharoplast) of a flagellate. The latter element is the smaller and more deeply staining, and is usually placed at the periphery, transversely to the longer axis of the oval organism. There is sometimes a very short, slightly curved filament to be seen, which may be a rhizoplast. Multiplication takes place by binary or multiple fission. The presence of the parasite used to be demonstrated by splenic or hepatic puncture; nowadays it can be demonstrated in peripheral blood, _e.g._, of the finger, or by culture of infected blood.

_L. donovani_ can be cultivated in citrated splenic blood, under aerobic conditions, at 22° to 25° C. This was first accomplished by Rogers (1904). It is not so easily culturable as _L. infantum_ on the Novy-MacNeal-Nicolle medium.[124] _L. donovani_ is inoculable with some difficulty into experimental animals--in India, white rats, white mice, dogs and monkeys (_Macacus spp._), have been inoculated. The Sudan variety, somewhat less virulent, is inoculable to monkeys. Row also produced a local lesion in _Macacus sinicus_ by subcutaneous inoculation of _L. donovani_. Parasites taken from such a local lesion were found to be capable of producing a generalised infection in _Macacus sinicus_ and white mice.

[124] For the composition of this medium, see Appendix.

In cultures the various species of _Leishmania_ all grow into herpetomonad, uniflagellate organisms (fig. 50, 10), about 12 µ to 20 µ in body length. On this account Rogers[125] and Patton place the Leishman-Donovan body within the genus _Herpetomonas_. The method of culture may be used in diagnosing leishmaniases.

[125] _Proc. Roy. Soc._, B, lxxvii, p. 284.

Kala-azar is very probably an insect-borne disease. Patton[126] suspects the bed-bug to be the transmitter and finds (fig. 50, _4_-_6_) that the Leishman-Donovan body can develop into the flagellate stage in the digestive tract of the bed-bug. Feeding experiments are unsatisfactory, since there are very few cases in which the parasites occur in sufficient numbers in the peripheral blood to make the infection of the insect possible, or at any rate easy. In examining the alimentary tracts of insects for possible flagellate stages of _Leishmania_, it must be remembered that in many insects natural flagellate parasites, belonging to the genus _Herpetomonas_, may occur therein; such natural insect flagellates may be harmless, and have no connection with the life-cycle of _L. donovani_. Natural herpetomonads are known to occur in the alimentary tracts of flies, mosquitoes, sand-flies, fleas and lice, but not in bed-bugs. Further, if such flagellates are able to be inoculated into and live within vertebrate hosts, producing symptoms like those of leishmaniasis, the origin of kala-azar is indicated (see pp. 104, 112).

[126] _Sci. Mem. Govt. India_, Nos. 27, 31 (1907–08).

*Leishmania tropica*, Wright, 1903.

Syn.: _Helcosoma tropicum_, Wright, 1903; _L. wrighti_, Nicolle,
1908; _Ovoplasma orientale_, Marzinowsky and Bogrow.

It is believed by some that the parasite was first described by
Cunningham in 1885, and studied by Firth in 1891, being called by
him _Sporozoon furunculosum_. If these earlier studies were of the
parasite, then its correct name is _L. furunculosa_, Firth, 1891.

The benign disease produced by this parasite has received many names, among the best known being Oriental sore, Tropical sore, Delhi boil and Aleppo button. These names, however, are not happy ones, as cutaneous leishmaniasis (_e.g._, on the ear) is now known to occur in the New World, for example in Mexico, Venezuela, Brazil and neighbouring States. However, it may be necessary to subdivide cutaneous leishmaniases later.

In the Old World the disease occurs in India, Persia, Arabia and Transcaucasia. It is also known in Algeria, Northern Nigeria, Egypt, Sudan, Crete, Calabria, Sicily and Greece.

The boils often occur on the face, and before ulceration the parasites may be found in the cells at the margin and floor of the “button.” In searching for parasites the scab should be removed and scrapings made from the floor and edges. Where lesions occur atrophy of the epidermis takes place, and infiltration of mononuclear cells (_e.g._, plasma cells, lymphoid and endothelial cells) follows. The parasites are intracellular, being found inside mononuclear cells. In non-ulcerating sores, Cardamitis found some free parasites. Non-ulcerating forms are said to occur in the Sudan. In the Old World the sores are often limited to exposed surfaces of the body. Infection of mucous membranes (such as the lip, palate, buccal and nasal membranes) may occur, especially in South America, and are often known there as “Espundia.” Christopherson (1914) has recorded a case in Khartoum.

_Leishmania tropica_ is equally well cultivated on Novy-MacNeal-Nicolle medium or on citrated blood. The usual temperature for cultivation is 22° to 28° C., though Marzinowski claims to have cultivated the parasite at 37° C. _L. tropica_ can be inoculated into monkeys and dogs, with the production of local lesions. Material from a human sore or flagellates from a culture may be thus successfully inoculated. Also infected material may be rubbed directly into a scarified surface. The incubation period is long, extending over several months. The duration of the disease may be from twelve to eighteen months. Recovery from one attack of tropical sore confers immunity, and the Jews in Bagdad inoculate their children with the disease on a part of the body which will be covered, and so secure immunity in adult life.

The mode of transmission of _L. tropica_ is unknown. Wenyon (1911)[127] has found that the parasite develops into the flagellate stage in the digestive tract of _Stegomyia fasciata_ in Bagdad. Patton (1912)[128] has found similar development in the bed-bug in Cambay. The house-fly, _Phlebotomus_ and _Simulium_ have been suspected as transmitters in different parts of the world.

[127] _Parasitology_, iv, p. 387.

[128] _Sci. Mem. Govt. India_, No. 50.

An interesting announcement has been made recently (May, 1913), that Neligan has found that _L. tropica_ occurs in dogs in Teheran, Persia, producing ulcers on the dogs’ faces (_cf._ natural occurrence of _L. infantum_ in dogs--see p. 110). Yakimoff and Schokhor (1914),[129] have found the disease in dogs in Tashkent.

[129] _Bull. Soc. Path. Exot._, vii, p. 186.

Gonder[130] (1913) has performed some interesting experiments showing the relation of infantile kala-azar to Oriental sore. Gonder infected mice with _L. infantum_ and with _L. tropica_. He used culture material and injected intraperitoneally or intravenously. In each a general infection resulted, with enlargement of the liver and spleen. Later, however, mice injected with Oriental sore (North African variety) developed peripheral lesions on the feet, tail and head, and the lesions contained _Leishmania_. No such peripheral lesions developed in the case of the mice infected with the kala-azar virus. Gonder suggested that Oriental sore, like kala-azar, is really a general infection overlooked in its earlier stages, and that it is in the later stages that peripheral lesions on the skin are developed. Row (1914)[131] also obtained a general infection in a mouse by the injection of cultures of _L. tropica_ from Oriental sore of Cambay.

[130] _Arch. f. Schiffs- u. Trop. Hyg._, xvii, p. 397.

[131] _Bull. Soc. Path. Exot._, vii, p. 272.

*Leishmania infantum*, Nicolle, 1908.[132]

Infantile splenic anæmia has been long known in Italy. It also occurs in Algeria, Tunis, Tripoli, Syria, Greece, Turkey, Crete, Sicily, Malta,[133] Spain and Portugal. This leishmaniasis is, then, distributed along the Mediterranean littoral; also in Russia. Cathoire (1904) in Tunis and Pianese (1905) in Italy were among the first to see the parasite. Nicolle then found the parasite in patients in Tunis, and further found spontaneous infection in dogs. The patients are usually children between the ages of 2 and 5 years. There are a few cases known in which the infantile type of leishmaniasis occurred in youths and adults of the ages of 17 to 19, while one patient in Calabria was 38 years old. The symptoms are like those of Indian kala-azar. Several Italian investigators and others consider that _L. infantum_ is the same as _L. donovani_, and that the latter name should be used for the parasite of Mediterranean leishmaniasis. This view, as to the identity of _L. donovani_ and _L. infantum_, seems coming into general favour.

[132] _Arch. Inst. Pasteur Tunis_, i, p. 26.

[133] _See_ Wenyon (1914), _Trans. Soc. Trop. Med. and Hyg._, vii, p. 97; also Critien (1911), _Annals Trop. Med. and Parasitol._, v, p. 37.

There are, however, differences between the Indian and infantile kala-azars, in addition to the ages of the patients affected, thus: (_a_) As regards cultures, it is found that _L. infantum_ is readily grown on the Novy-MacNeal-Nicolle (“N.N.N.”) medium (saline blood-agar), and that sub-cultures are easily obtained; in citrated blood _L. infantum_ grows with difficulty. The reverse is the case with regard to culture media for _L. donovani_, which grows with difficulty on the N.N.N. medium, but relatively easily in citrated splenic blood. (_b_) Considering inoculability into experimental animals, it is found that _L. donovani_ is inoculated generally with some difficulty into white rats, white mice and monkeys, and with greater difficulty into dogs, while _L. infantum_ can be inoculated into several experimental animals, especially into dogs and monkeys, with ease. (_c_) At present _L. donovani_ is not known to occur spontaneously in animals, but _L. infantum_ is found naturally in dogs in the Mediterranean region, and the disease in dogs is often referred to as canine kala-azar. Kittens have occasionally been found infected. However, these differences must not be emphasized too much.

The material for cultivation is obtained from punctures of spleen, liver or bone-marrow of cases infected with _L. infantum_. It is not always easy, however, to infect from cultures, as the cultural flagellates inoculated into the body are often phagocytosed.

Similarly, the material for animal inoculation is obtained from emulsions of infected spleen, liver or bone-marrow. Dogs and monkeys are easily inoculated with such material; Nicolle inoculates into the liver or the peritoneal cavity. Mice, white rats, guinea-pigs and rabbits only show slight infections after such inoculations.

Dogs infected experimentally with infantile leishmaniasis may show either acute or chronic symptoms. The acute course occurs more often in young dogs, and is usually fatal in three to five months. The chronic course is found more commonly in older dogs, and may last seventeen to eighteen months. In acute forms there is irregular fever, progressive wasting, diarrhœa occasionally, motor disturbances involving the hind quarters, and the animal dies in a comatose condition. In the chronic form the animal may appear well, except for loss of weight. The parasites may be found in the internal organs of these experimental dogs, but are not numerous in the peripheral blood except at times of high fever. Experimental monkeys live about three months.

It may be interesting to record the number of dogs found to be infected naturally with leishmaniasis in various countries. In Tunis, Nicolle and Yakimoff found about 2 per cent. infected out of about 500 dogs examined. Sergent in Algiers found 9 infected out of 125 dogs examined. In Italy and Sicily, Basile found about 40 per cent. of the dogs to be infected out of 93 examined at Rome and Bordonaro. Cardamitis found 15 infected out of 184 examined in Athens. In Malta, Critien found 3 infected out of 30 dogs examined. Alvares found 1 infected dog out of 19 examined in Lisbon. Pringault has recently (December, 1913) found an infected dog in Marseilles.[134] Yakimoff and Schokhor found 24 per cent. infected out of 647 dogs examined in Turkestan.

[134] _Bull. Soc. Path. Exot._, vii, p. 41.

The distribution of the parasites in the body of the human patient is much the same as in the case of Indian kala-azar. Critien records the finding of parasites in the mucous flakes of the stools of a three-year-old Maltese child.[135] Intestinal lesions rarely occur in infantile leishmaniasis.

[135] Quoted by Leishman (1911) in his interesting review of Leishmaniasis, _Journ. Roy. Army Med. Corps_, xvii, p. 567, xviii, pp. 1, 125. Also _Quart. Journ. Med._ v, pp. 109–152.

_Ætiology._--Infantile leishmaniasis is stated to be transmitted by fleas, especially dog fleas, _Ctenocephalus canis_ (= _Pulex serraticeps_), and by _Pulex irritans_. Children living in contact with infected dogs may be bitten by infected dog fleas, and so contract the disease. Basile (1910–11) and Sangiorgi (1910) state that they found _L. infantum_ parasites in the digestive tract of the dog flea. After searching they found infected dog fleas on the beds, mattresses, and pillows used by children suffering from the disease. Franchini (1912) thinks that _Anopheles maculipennis_ may be concerned in the transmission.

Basile[136] tried a number of experiments to show that infantile leishmaniasis is transmitted by fleas, thus:--

[136] Numerous papers in _Rendiconti R. Accad. dei Lincei_ (Rome), xix, xx (1910–11).

(1) Fleas were taken from a healthy dog. They were placed in vessels containing infected spleen-pulp and allowed to feed thereon. The fleas were then killed and dissected, and portions of the gut-contents examined for parasites. The remainder of the gut was emulsified and injected into a young puppy, whose bone-marrow had been shown previously to be uninfected. Basile states that the puppy became infected. The parasites are said to increase in number in the flea’s gut.

(2) Two healthy pups, each a month old, and born in the laboratory, were placed in a disinfected, flea-proof cage. A few days after, an infected dog was placed in the cage, so that fleas from the infected dog could pass on to the puppies. A month later the two pups became infected, parasites being found in them after liver puncture. A number of control puppies from the same litter remained uninfected and in good health.

(3) Basile next used other laboratory-born puppies, a month old. Four of the litter were placed in a disinfected, flea-proof gauze cage in Rome. The cage was isolated from other dogs. Fleas obtained from an infected area in Sicily were placed in the cage. The puppies were examined by hepatic puncture, but were found to be negative for two months. Then two of the puppies showed infection, and six days later the remaining two puppies were found to be infected, and all four died. They showed irregular temperatures, and were getting thin. Control puppies remained healthy.

From these experiments Basile concludes that fleas transmit leishmaniasis. However, Basile did not exclude the possible occurrence of natural herpetomonads in the gut of the fleas.[137] _Herpetomonas ctenocephali_ is known to occur in the gut of _Ctenocephalus canis_. A natural _Herpetomonas_ is also known in the gut of _Pulex irritans_, as well as a _Crithidia_ (_C. pulicis_, Porter). These natural flagellates of the fleas pass through non-flagellate stages, like the Leishman-Donovan body. In consequence Wenyon and Patton, among others, have criticized Basile’s results. Further, other investigators, such as Wenyon and Da Silva (1913), have repeated Basile’s flea experiments and been unable to confirm them.

[137] See Fantham, _Brit. Med. Journ._, 1912, ii, p. 1196.

In feeding and inoculation experiments the incubation period of the parasite may be long, and so it is necessary to wait a long time to see whether the parasite will develop.

_Immunity._--Nicolle has tried some experiments with _L. infantum_ and _L. tropica_. He finds that in animals recovery from an attack of the former confers immunity against infection by the latter and vice-versâ.

Laveran[138] records that a monkey having an immunity against _L. infantum_ was also immune to _L. donovani_.

[138] _Annales Inst. Pasteur_ (1914–15), xxviii, pp. 823, 885; xxix, pp. 1, 71.

As mentioned on p. 103, Laveran and Franchini (1913), working in Paris, have succeeded in inoculating _Herpetomonas ctenocephali_, a natural flagellate in the gut of the flea, _Ctenocephalus canis_, into white mice. Leishmaniform stages of the flea flagellate were recovered from the peritoneal exudate, blood and organs of the mice some weeks after inoculation. The parasites may also be conveyed by way of the digestive tract of the vertebrate. Similar experiments have succeeded with _H. pattoni_. These experiments go to show, together with those of Fantham and Porter with _H. jaculum_ (see p. 104), that, in the words of the latter authors, “it may be expected that the various leishmaniases, occurring in different parts of the world, will prove to be insect-borne herpetomoniases.”

Genus. *Histoplasma*, Darling, 1906.

Under the name _Histoplasma capsulatum_,[139] Darling described small round or oval parasites, enclosed in a refractile capsule, and each containing a single nucleus. The bodies were found in cases of splenomegaly in Panama. They occurred in the endothelial cells of the small blood-vessels of the liver, spleen, lungs, intestine and lymphatic glands, and also within the leucocytes. A few flagellates were stated to occur in the lungs. The parasite has usually been placed near _Leishmania_, but recently Rocha-Lima has stated that _Histoplasma_ is a yeast.

[139] _Journ. Amer. Med. Assoc._, xlvi, p. 1283: _Journ. Exptl. Med._ (1909), xi, p. 515.

Genus. *Toxoplasma*, Nicolle and Manceaux, 1908.

The genus was created for crescentic, oval or reniform parasites,
2·5 µ to 6 µ by 2 µ to 3 µ, possessing a single nucleus and
multiplying by binary fission. They occur in mononuclear and
polymorphonuclear cells in the blood, spleen, liver, peritoneum etc.
(fig. 51). The parasites have been found in the gondi, dog, rabbit,
mole, mouse, pigeon and other birds. Although various species names
have been given to the parasites in these hosts, it seems probable,
from cross infection experiments, that there is but one species with
several physiological races. Splendore[140] (1913) has described a
flagellate stage.

[140] _Bull. Soc. Path. Exot._, vi, p. 318.

in spleen. [1 is about the size of a red blood corpuscle, as drawn in the figures]. Magnification not stated. (After Castellani.)]

Castellani (1913–14)[141] has described similar parasites from a case of splenomegaly, with fever of long standing, in a Sinhalese boy. The bodies were found in the spleen and more rarely in the blood (fig. 52). Castellani has named them _Toxoplasma pyrogenes_. Further researches are needed.

[141] _Journ. Trop. Med. and Hyg._, xvii, p. 113.

THE SPIROCHÆTES.

The Spirochætes are long, narrow, wavy, thread-like organisms, with a firm yet flexible outer covering or periplast. There is a diffuse nucleus internally in the form of bars or rodlets of chromatin distributed along the body. In some forms there is a membrane or crista present (fig. 53), which in the past was compared with the undulating membrane of a trypanosome, but the membrane of a spirochæte does not undulate. Progression is very rapid, corkscrew-like and undulatory movements occurring simultaneously.

The genus _Spirochæta_ was founded by Ehrenberg in 1833 for an organism which he discovered in stagnant water in Berlin. Ehrenberg named the organism _Spirochæta plicatilis_. According to Zuelzer (1912) _S. plicatilis_ does not possess a membrane or crista, but an axial filament. _S. gigantea_ has been described by Warming from sea-water.

Spirochætes occur in the crystalline style and digestive tract of many bivalve molluscs. The first molluscan spirochæte to be studied was that of the oyster, named by Certes (1882) “_Trypanosoma_” _balbianii_ (fig. 53). Similar spirochætes, probably belonging to the same species, occur in various species of _Tapes_ and in _Pecten_ (the scallop). _S. balbianii_ has rounded ends (fig. 53). Other spirochætes occur in freshwater mussels (_Anodonta_ spp). _S. anodontæ_, studied by Keysselitz (1906) and by Fantham (1907), has pointed ends. Gross (1911) suggested the generic name _Cristispira_ for molluscan spirochætes, because they possess a well-marked membrane or “crista,” which appears to be absent from _S. plicatilis_, according to Zuelzer’s researches.

Schaudinn in 1905 founded the genus _Treponema_ for the parasite of syphilis (_T. pallidum_), discovered by him and by Hoffmann. According to Schaudinn the Treponemata have no membrane or crista. The pathogenic agent of yaws or frambœsia, discovered by Castellani, is also placed in the genus _Treponema_, as _T. pertenue_.

There remain the blood spirochætes. It is somewhat disputed as to whether these organisms possess a membrane. The present writer considers that they have a slight membrane or crista. The name of the genus in which to place the blood-inhabiting forms is somewhat uncertain and disputed. Various generic names given to them are _Spirochæta_, _Treponema_, _Spiroschaudinnia_ (Sambon) and _Borrelia_ (Swellengrebel). Included in this division are the causal agents of relapsing or recurrent fever. These Protists will be named, for description, Spirochætes without prejudice as to the ultimate correct generic name.

It is sometimes made a matter of argument as to whether the spirochætes are Protozoa or Bacteria. Such arguments are somewhat unprofitable. Morphologically the spirochætes are like the Bacteria in possessing a diffuse nucleus. They differ from _Spirillum_, an undoubted bacterial genus, in being flexible and not possessing flagella. Molluscan spirochætes, however, may appear to have flagella if their membrane becomes frayed or ruptured, when the myonemes therein (fig. 53), becoming separated, form apparent threads or flagella (Fantham, 1907–08).[142]

[142] _Quart. Journ. Microsc. Sci._, lii, p. 1.

Again, the mode of division of spirochætes has been used as a criterion of their bacterial or protozoal affinity. They have been stated to divide transversely, longitudinally, and by “incurvation,” or bending on themselves in the form of a *U*, “a form of transverse fission.” The present writer believes that they divide both transversely and longitudinally, and that there is a periodicity in their mode of division at first longitudinal (when there are few spirochætes in, say, the blood) and then transversely (when spirochætes are numerous in the blood).[143] Some authors consider that longitudinal division is explained by “incurvation.”

[143] _Proc. Roy. Soc._, B, lxxxi, p. 500.

The spirochætes of relapsing fever show a remarkable periodic increase and decrease in numbers in the blood. They are transmitted by ticks or by lice. They react to drugs (_e.g._, salvarsan or “606”) rather like trypanosomes, and--like Protozoa, but unlike Bacteria--they are cultivated with difficulty. These and other criteria have been used to endeavour to determine whether they are Protozoa or Bacteria. The present writer believes that they are intermediate in character, showing morphological affinities with the Bacteria and physiological and therapeutical affinities with the Protozoa. The group Spirochætacea, as an appendix to the Protozoa, has been created for them by the present writer (Jan., 1908). Others have placed them in the Spirochætoidea of the Bacteria or with the Spirillacea. Doflein (1909) called them Proflagellata. Further discussion is unnecessary, as they are undoubtedly Protista (see p. 29).

There is no true conjugation, sex or encystment in spirochætes, but morphological variation may occur.[144] They may agglomerate.

[144] Fantham, _Parasitology_, ii, p. 392.

The Spirochætes form an interesting chapter in the evolution of parasites. There are free living forms, parasitic forms in the guts of both vertebrates and invertebrates, and blood-inhabiting forms. These probably represent the order of evolution of parasitism. The blood-inhabiting forms are pathogenic to warm-blooded hosts.

We must now consider the blood Spirochætes and the Treponemata (organisms of syphilis and of yaws).

THE SPIROCHÆTES OF THE BLOOD.

There are at least two important human parasites included hereunder:--

(_a_) _Spirochæta recurrentis_ (=_S. obermeieri_), (_b_) _Spirochæta duttoni_.

More is known of the life-cycle of _Spirochæta duttoni_, and it will be convenient to consider that first.

*Spirochæta duttoni*, Novy and Knapp, 1906.

The specific name _duttoni_ was also given, independently, to this
parasite in 1906 by Breinl and Kinghorn.

_S. duttoni_ is the pathogenic agent of African tick fever in man, prevalent in the Congo State and other parts of Africa. The full-grown organism is about 16 µ to 24 µ long, and has pointed ends. It is 0·25 µ to 0·5 µ broad. P. H. Ross and Nabarro were among the earliest to see a spirochæte in the blood of patients in Uganda. It is transmitted by the tick, _Ornithodorus moubata_.

In the blood of the patient some of the spirochætes may show, after staining, lighter and darker portions (chromatin dots) and evidence of the possession of a very narrow membrane (fig. 54). The mode of division has already been discussed. Periodicity in the direction of division was first described by Fantham and Porter,[145] (1909). Just before the crisis in African tick fever, Breinl has stated that _S. duttoni_ becomes thinner in the spleen and bone-marrow and rolls up into skein-like forms, which are surrounded by a thin “cyst” wall (probably the periplast). Such occur in apyrexial periods. Inside the cyst the spirochæte breaks up into granules. Balfour and Sambon have described somewhat similar rolled up forms, breaking into granules, inside the red blood cells of Sudanese fowls in the case of _S. granulosa_ (possibly only a variety of _S. gallinarum_). The intracorpuscular stage is not definitely established.

[145] _Proc. Roy. Soc._, B, lxxxi, p. 500.

The granule phase, however, is an essential one in the invertebrate transmitter (fig. 54_c_). In 1905,[146] Dutton and Todd proved experimentally that _O. moubata_ transmitted _S. duttoni_. They fed ticks, obtained from Congo native huts in which infected persons lived, on monkeys and the latter became infected. Dutton and Todd also found the offspring of infected ticks to be capable of transmitting the infection to experimental animals. They concluded that _O. moubata_ was a true intermediate host.

[146] _Liverpool Sch. Trop. Med._, _Memoir_ xvii; _Lancet_, Nov. 30, 1907, p. 1523.

A little later in 1905, Koch stated that spirochætes from the gut of the tick penetrated the gut wall and tissues and found their way into the eggs in the ovary. Koch figured tangled masses of spirochætes as occurring in the tick eggs. He found ticks infective to the third generation. He thought that the infection was spread by the salivary fluid of the tick, in the act of biting. (This is now known to be incorrect.) Markham Carter (1907) corroborated Koch’s work on the spirochætes in the tick eggs, and they have been seen since by Kleine and Eckard (1913).

Sir William Leishman,[147] in 1909–10, found that at ordinary temperatures the salivary glands of infected ticks (_O. moubata_) were not themselves infective, and that the infection occurred by way of the ticks’ excretion. The spirochætes (contained in the ticks’ excrement) found their way into the vertebrate host through the wound made by biting. While feeding, ticks pass large quantities of clear fluid from the coxal glands; in this fluid an anticoagulin occurs. Some of the ticks also pass thick, white Malpighian secretion, that is, excrement, towards the end of the feed. Leishman, using experimental monkeys, showed that if infected ticks were interrupted while feeding, then no infection resulted in the monkeys. If, however, the ticks were allowed to finish their feed, and the Malpighian secretions were passed, then the experimental monkeys became infected. Fantham[148] and Hindle[149] (1911), independently, have repeated the experiments with mice.

[147] _Journ. Roy. Army Med. Corps_, xii, p. 123; _Lancet_ (1910), clxxviii, p. 11.

[148] _Annals Trop. Med. and Parasitol._, v, p. 479.

[149] _Parasitology_, iv, p. 133.

Leishman’s methods and results may be summarized thus: Saline emulsions of the organs of infected ticks were made, after the organs had been most carefully dissected out. The ticks were first kept for several days at certain constant temperatures, such as 24° to 25° C. or blood heat, 37° C. The saline emulsions of the organs were inoculated, separately, into experimental animals, and the results recorded:--

At 24° C. At 37° C.
Salivary glands Negative Positive
Malpighian tubules Positive Positive
Gut and contents Positive Positive
Excrement Positive Positive
Genital organs Positive Positive

Coxal fluid is usually negative; thick, white excrement from Malpighian tubes is positive.