Trypanosomic Diseases Found in Animals

List of five major trypanosomic diseases found in animals:- 1. Dourine 2. Nagana 3. Surra 4. Mal-De-Caderas 5. Leishmaniasis.

Trypanosomic Disease # 1. Dourine:

Synonym:

Infectious polyneuritis, Cover­ing disease, Breeding paralysis.

Definition:

This is a chronic contagious infective disease affecting horses and asses characterised by local inflammation of external genital organs followed by cutaneous eruptions known as Dourine plaques and paralysis. It is caused by Trypanosoma equiperdum, a monomorphic trypanosome resembling T. evansi. In­fection takes place by coitus, the organisms being able to pass through intact mucosa.

Pathogenesis:

T. equiperdum is rarely found in the blood of the horse. It is found in the fluid contents of the swellings of the skin (dollar plaques), in the mucous discharge from the ure­thra and vagina, as well as, in fluid obtained by puncture of the testicle. During copulation, infec­tion occurs from the secretions of the urethra and vaginal mucosa of diseased stallions and mares, the trypanosomes being able to penetrate intact mucous membrane.

Incubation period:

1 to 4 weeks or it may be much longer.

Symptoms:

Two definite stages of the dis­ease are recognised:

1. Primary stage:

In case of stallions, oedematous swelling of the prepuce, penis and testicles, redness and swelling of urethral mu­cosa, a slight muco-purulent discharge and swell­ing of the inguinal lymph glands. In mares, oedematous swelling of the vulva, redness and swelling of vaginal mucosa and mucopurulent discharge from vagina. Increased sexual excite­ment is observed in both sexes.

2. Secondary stage:

Formation of urticaria-like plaques on the skin – Dollar plaques or Dourine plaques. These are round, flat swellings 2 to 5 cm in diameter, located on any part of the body or neck. They are pathognomonic of dourine and may come and go in series. The skin of the external genital may be depigmented. The nervous symptoms consist of motor paraly­sis, facial paralysis and sacral paralysis. Paralysis and prolapse of penis are commonly seen.

Sub­-maxillary lymph glands may be swollen, nasal catarrh and fever may be present. Emaciation is a characteristic symptom and usually begins at glu­teal muscles and extends rapidly.

Course:

It is chronic in cool climate and acute in tropical climate.

Mortality:

50 to 75 per cent.

Diagnosis:

It is made by complement-fixa­tion examination of the blood.

Treatment:

Same as Surra except Tartar emetic.

Trypanosomic Disease # 2. Nagana:

Synonym:

Tse-tse fly disease.

Definition:

This is an acute or chronic infective disease of all domesticated animals, spe­cially enquiries in Africa, caused by Trypanosoma brucie.

Etiology:

Trypanosoma brucei is a polymoiphic tryp, the flagellar form resembling T. evansi; arid other form being short, broad and stumpy. Two other tryps are associated with this disease land these are T. congolense and T. vivax. The organisms are transmitted by Tse-tse flies — Glossina morsitans, G. longipalpalis and G. palpalis, transmission being both mechanical and following a cyclical development in the fly.

Symptoms:

At first there is a high fever, marked congestion of the mucous membranes and oedematous swellings of the limbs, abdomen, eyelids and sub-maxillary region. The course is usually chronic over a period of one to several months, during which period, there are irregular fever, anaemia, icterus, emaciation and urticaria. Many trypanosomes are present in the blood.

Incubation period:

2 to 10 days.

Treatment:

Intravenous injection of Bayer – 205. Naganol for large animals and Tryparsamide for dogs are the treatment.

Murrina:

Definition:

Murrina is a South American trypanosomiasis which closely resembles Surra.

Etiology:

It is caused by Trypanosoma hippicum that cannot be distinguished from T. evansi.

Mode of infection:

It is transmitted by flies and the vampire bat — Desmodus rotundus. Cattle are not affected but they may carry the trypanosome in their blood.

Incubation period:

5 days.

Symptoms:

The disease begins with de­pression, weakness and fever. Oedema and fever are recurrent throughout the course, haemoglo­binuria is frequent and death occurs in from 2 to 3 months.

Treatment:

Intravenous infection of Bayer- 205.

Trypanosomic Disease # 3. Surra:

Synonym:

Rotten disease; Tribasha (Camel.)

Definition:

This name is given to a disease of domesticated animals caused by Trypanosoma evansi and marked by fever. Petechiae of mucosa, Oedema of dependent parts, progressive anaemia and emaciation ending in death if left untreated.

Protozoology:

T. evansi is a monomorphic trypanosome with a free-ending flagellum by which it manifests active movement. It measures 25 to 33^µ long by 1.5 to 2.5^µ wide. This is an extracellular protozoal parasite provided with a nucleus, the Kinetoplast and a flagellum at the anterior or pointed end of the body.

Incidence:

As would be expected from a disease transmitted by biting flies, it is prevalent at the close of and immediately following the rainy season and on low marshy land and along streams with tall vegetation that may harbour the vector fly — Tabanidae. The period when the disease is most prevalent is known as Surra sea­son and the areas where the disease is so preva­lent — as Surra zones. In India, the surra season is usually from August to January.

In regions where it is indigenous, Surra is usually mild or subclinical among the native ru­minants, but may be fatal or destructive when introduced into new areas.

Animals susceptible:

Equines are most susceptible and then comes camels and elephants. Then in order comes cattle, buffaloes, sheep, goats and native dogs.

Although, camels commonly carry the infec­tion in their blood and serve as a reservoir with­out exhibiting clinical symptoms, yet under spe­cial circumstances, mortality among them may be very high. Mortality approaches 100 per cent amongst solipeds when introduced into new ar­eas.

Modes of infection:

By inoculation through the bites of the biting flies, the most common of which is Tabanus. Other flies which also act as vectors are Stomoxys, Haematopona and even the common house fly.

Certain ticks of the genus Orinthodorus have been found to transmit trypanosomes experimen­tally.

Dogs get infected by fleas or by ingestion of infected flesh.

The tryps are conveyed by the vectors may be in a mechanical way, i.e. carried directly from an infected animal to an uninfected one by the bite of a blood sucking fly or cyclical. When the insect host is not infective for a definite time after ingestion of the parasite. In this case, the parasite passes a definite part of its life-cycle in the fly. In many cases, transmission may be both mechani­cal and cyclical. Tryps also quickly die after the death of their host, whose blood is not infective after 24 hours.

Pathogenesis:

In the blood of mammalian host the tryps reproduce by splitting lengthwise (longitudinally). Pathogenic tryps exert their ac­tion indirectly through their elaboration of .toxic substance (the nature of which has not yet been definitely isolated) which cause destruction of RBC with resultant anaemia.

After infection, there follows a periodical accumulation of tryps in the blood usually accompanied by a rise of temperature lasting for 3 or 4 days. They then disappear rapidly, during which developing forms may have matured in certain organs (spleen and bone marrow), when after 1 to 8 days, they again appear in the blood in large number giving rise to fever again.

Incubation period:

3 to 14 days, 10 days on an average.

Postmortem lesions:

In addition to the effects of emaciation, anaemia and other signs of general ill health, there may be yellow, gelatinous infiltration of the subcutis. Serous exudation in the pericardium and abdominal cavity, small haemorrhages in the serous and muco-membranous (petechiae) are seen. A variable degree of enlargement of the spleen and lymphatic glands. There may be areas of congestion in the stomach and intestines.

Symptoms:

(In Solipeds) — In solipeds in which the disease is most severe, the disease commences with a rise of temperature — 104° F (40°C) or over, which is of a recurrent nature; the pyrexia lasting for 3 to 4 days with intermission of 1 to 8 days. Pronounced lassitude and weakness, ap­pearance of petechiae on the mucosa specially on the conjunctiva, urticarial eruptions and Oematous swellings on the limbs, external genital organs, sub-maxillary area, lower abdomen.

The disease may be fatal during the early days, but as a rule, a marked improvement takes place after some days, soon followed by a recur­rence of the fever.

The animals gradually becomes weaker, the mucosa become pallor and icteric, superficial lymph glands become enlarged, respiration be­comes rapid, laboured and in spite of an un­changed appetite, the animals become gradually emaciated and finally go down when they are unable to rise (once a surra case is down, it can never rise) and die with symptoms of marked dyspnoea.

Course:

In horses, it is from 1 to 2 months usually. Rarely 1 to 2 weeks or as long as 3 to 4 months.

(In Cattle):

The disease is usually less severe and is manifested by all the symptoms stated above but in milder form, with addition of lachrymation and paresis of hind quarters. In the majority of cases, recovery eventually takes place, some of the recovered animals remain as carriers.

The disease sometimes runs a very acute course in cattle in which the animals suddenly manifest symptoms consisting of rapid rise of temperature, acute congestion of mucous mem­branes, laboured respirations, sometimes diar­rhoea and bleeding from the nose> and ears fol­lowed by death in a few hours. This form, how­ever, is very rare.

(In Buffaloes and Zebus):

Although, these animals often harbour the parasites in their blood, they seldom present symptoms. When they do, it is very mild and chronic.

(In dogs):

The disease usually appears among the imported sporting dogs which always ends fatally. The native pariah dogs are rarely affected and then only mildly.

(In camel):

The disease may sometimes presents acute symptoms, but it usually occurs in them in mild form showing much the same syn­drome as in horses, which runs a chronic course usually lasting about 3 years and that is why it is known as “Tribasha” in camels.

The majority of cases are eventually fatal, but some may recover and remain as carriers for years.

Diagnosis:

Detection of trypanosomes in the blood by microscope. It must be remembered that they are only found in blood during the febrile period and disappear during intermission.

When the blood is negative, examination of fluid obtained by puncturing an enlarged lymph gland may prove positive.

In horses, one or two examinations of blood usually enable one to diagnose a case, but in cattle with mild course usually, several examina­tions may be necessary to confirm the diagnosis.

In camels, a diagnosis is often difficult and for this Formal-gel test and mercuric chloride test have been devised.

Treatment:

Naganol or Bayer’s 205 is de­cidedly the best chemotherapeutic agent.

Its dose for large animals are:

Camel, horses, cattle:

5 gms/500 kg body weight in a 10% solution given intravenously. A single dose in the early stage of the disease is sufficient to effect a cure, but an animal in the late stage of the disease will require two similar doses at an interval of a week or 15 days.

Antrypol (B. D. H.) given in the similar way as Naganol is also reported to be a good remedy. Antrypol is best made into a’ solution with 5% glucose to avoid the toxic effects that follows its administration.

Tryparsamide (M & B) is also reported to be very effective. The dose is 0.03 gm/kg body weight made into 20% solution for intramuscular injection or 10% solution injection for subcutane­ous injection.

In cattle, in which the disease is not so acute, Tartar emetic has been tried with much success. The dose recommended by Edwards (I. V. R. I.) is 5 ml per 50 kg body weight of a 3.2% solution given .intravenously every 5th day up to 6 injec­tions.

In hunting dogs such as fox hounds, the dose of Naganol or Antrypol is 5 ml of a 10% solution given intravenously and repeating after an inter­val of 3 weeks to 1 month.

Antrycide:

A very effective trypanosomicidal agent is reported to have eclipsed all other agents in the treatment of Trypanosomiasis.

Trypanosomic Disease # 4. Mal-De-Caderas:

Definition:

This is a sub-acute or chronic infective disease of equines resembling Surra and occurring in South America.

Etiology:

It is caused by Trypanosoma equinum, which is monomorphic tryp resembling T. evansi.

Mode of infection:

Although the natural method of infection’ has not yet be determined, Tabanus and Stomoxys have been blamed as vec­tors.

Symptoms:

Progressive emaciation, weak­ness of the hind quarters and staggering gait.

Treatment:

Intravenous injection of Bayer- 205 or Naganol.

Trypanosomic Disease # 5. Leishmaniasis:

Definition:

Leishmaniasis is a disease characterised either (a) febrile anaemia with swell­ing of the spleen (Visceral leishmaniasis) or (b) by formation of boils on the skin followed by ulceration (Cutaneous leishmaniasis) and caused by L. donovani and L. tropica, respectively, which are morphologically indistinguishable.

Mode of infection:

Transmitted by blood­sucking sand flies — Phlebotomous.

N. B.:

This infection is of considerable importance in man, but not in animals other than the dog. Visceral leishmaniasis in man is called “Kalaazar” and cutaneous leishmaniasis is called “Oriental sore” and caused by L. donovani and L. tropica, respectively.

Postmortem lesions:

(In visceral leishmaniasis)

More or less pronounced acute or chronic enlargement of the spleen, strawberry coloration of bone marrow and signs of advanced emacia­tion and anaemia.

Symptoms:

It varies considerably. On the whole, there is moderate variation in tempera­ture, gradual emaciation, loss of weight and ana­emia which lead to complete exhaustion, result­ing in death after some months. In some cases, there is swelling of the abdomen due to enlarged spleen and accumulated effusions. In some other cases, there may be swelling of the lymph glands and periodical diarrhoea with paresis of hind­quarters towards the end.

(In cutaneous leishmaniasis) — Formation of boils followed by ulceration—generally around the nostrils, which sometimes may extend to na­sal mucosa.

Diagnosis: In visceral leishmaniasis:

Examination of fluid by puncturing the spleen and in case of cutaneous leishmaniasis — the secretion from the ulcer.

Treatment:

10 ml of 1% solution of Tartar – Emetic intravenously in case of visceral leshmaniasis. The same in cutaneous leishmaniasis plus local application of Antimony ointment.