Page 201 - The Veterinary Laboratory and Field Manual 3rd Edition

170 Susan C. Cork and Mani Lejeune

flies of the genus Tabanus sp., Stomoxys sp. and enlargement of the spleen and other internal
Hippobosca sp.), tsetse flies (Glossina sp.), kissing organs. Leishmania tropica causes mucocutane-
bugs (Reduviidae) or mechanically, and cause ous leishmaniasis. Both forms occur in the
a range of diseases in humans (for example, tropics but have also been seen more recently in
sleeping sickness in Africa and Chagas disease the Mediterranean region. In domestic animals,
in Latin America) and animals (for example, L. infantum is the most important which causes
nagana disease, Surra, and so on). Nagana, potentially fatal disease in dogs. This parasite is
caused by Trypanosoma congolense congolense, is the endemic in many continents.
most important trypanosome of cattle in tropi-
cal Africa. In many cases there may be mixed
infections with T. brucei and T. vivax. Trypanosoma other flagellates
congolense is widely distributed between 15ºN
and 25ºS. Hosts include cattle, sheep, goats, Trichomonads and Giardia sp. are mucosoflagel-
equids, camels, dogs and pigs. The wildlife reser- lates and are motile on mucosal surfaces. Giardia
voirs include antelope, giraffe, zebra, elephants sp. are frequently associated with diarrhoea in a
and warthogs. A similar condition is caused wide range of animals but may often be present
by T. brucei brucei, which can infect a similar in healthy animals with no evidence of disease.
host range. It currently occurs in sub-Saharan Severe enteritis may occur following heavy infec-
Africa between the latitudes 14ºN and 29ºS. tion with Giardia sp. especially where the host
Trypanosomosis and other diseases associated has concurrent disease. In some cases, cysts
with haemoparasites cause significant economic may remain in the gut wall long after recovery
loss in ruminants and other livestock, including or treatment but may re-activate when the host’s
horses, in tropical countries and are discussed in immunity is compromised.
more detail in Section 3.6.
Leishmania sp. protozoa cause a range of clini- Diagnosis
cal signs in humans as well as wild and domestic
animals and are transmitted by insect vectors. Diagnosis is by identification of trophozoites in
Leishmania donovani is responsible for human faecal smears. Faecal flotation tests for cysts (using
visceral leishmaniasis (kala-azar), which causes ZnSO as flotation fluid) and antigen capture
4
ELISA are used to diagnose Giardia sp. infection.
Trophozoites of Trichomonads (T. foetus, T. blag-
burni) can be cultured using specific in pouch.

Prevention and control

Prevention and control involves improved
hygiene and prevention of faecal contamination
of feed and water supplies.
Members of the group Trichomonads may
cause a range of diseases in various host spe-
cies. Tritrichomonas foetus can cause abortion in
Figure 3.35 Trypanosome (T) as seen in a Giemsa cattle and may be isolated from infected foetal
stained blood smear from a horse (1000× oil material, the uterus and vagina of the cow and
immersion). the prepuce, penis and epididymis of infected

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