Page 210 - The Veterinary Laboratory and Field Manual 3rd Edition

Parasitology 179

anaplasmosis and occasionally the organism can pasture. Additional strategies would include
be transmitted mechanically during veterinary the control of livestock movement and keeping
procedures for example, by use of contami- stock away from infected wildlife. Insects may
nated syringes and other equipment during also need to be controlled to prevent mechanical
vaccination or surgical procedures. transmission.

cLInIcaL SIGnS and dIaGnoSIS Trypanosomosis
Clinical signs are characterized by fever (tem-
perature > 40°C), loss of appetite, marked Trypanosomes are flagellate protozoa that live in
anaemia (mucous membranes are pale and the blood, bone marrow, lymph nodes and some-
may then become yellow as jaundice devel- times the nervous system of affected animals and
ops), haemoglobinuria (urine darkish yellow to in the digestive tract and salivary glands of the
brown) and enlargement of the lymph nodes. insect vector. Trypanosomiasis occurs through-
Animals usually lose condition rapidly and are out Africa, South America and many Asian
susceptible to the development of concurrent countries. Unlike the other haemoprotozoan dis-
disease. Diagnosis may be confirmed at necropsy eases discussed in this section, Trypanosomosis
although the gross findings resemble babesiosis is primarily transmitted by biting flies (tsetse
except that the urine in the bladder is usu- and other flies of the family Glossinae) and not
ally brown, not red. Ante-mortem diagnosis is by ticks. Trypanosomes come from a group of
based on the clinical signs, epidemiological pat- protozoan organisms which usually undergo
tern, the examination of stained blood smears part of their reproductive cycle in an intermedi-
for the presence of Anaplasma sp. and the use of ate host. Many domestic (cattle, sheep, goats,
serological tests. dogs, swine, mules, donkeys, camels and buf-
falo) and wild animals may become infected with
controL and PrEvEntIon one or more of the trypanosome species. The
The disease may be treated by using antibiotics following information refers mainly to African
(for example, tetracycline). Prevention is possible Trypanosomosis in cattle (‘nagana’ or tsetse fly
by implementing a vaccination program. Low- disease). Wild and domestic bovids (cattle, buf-
pathogenic A. centrale has been used effectively falo, eland, antelope) may be infected following
as a vaccine, as have killed vaccines. Vaccination a bite from an infected vector (tsetse fly). New
of all stock is rarely practical but calves exposed outbreaks of disease may develop if cattle in a
to infection can develop ‘premunity’ that pro- herd move into an infected tsetse fly area and
tects them in later life although these calves (as long as vectors are present) if wild (reser-
may remain carriers. The vaccination, along voir) hosts and/or asymptomatic carrier animals
with administration of hyperimmune serum, come into the same range as an immunologically
has also been used in treatment. Convalescent naïve herd.
animals must be well fed to ensure full recov-
ery. Adult animals recovering from an attack of LIFE cycLE and cLInIcaL SIGnS
the disease have a strong resistance to it which There are many species of Trypanosome (for
lasts for years. As with other tick-borne diseases, example, Trypanosoma congolense, T. vivax, T. brucei,
tick control is important and should include the T. evansi, T. equiperdum) and a number of specific
regular use of repellents, acaricides (dipping, disease conditions caused by each type. The
spraying, dusting) and the periodic rotation of clinical presentation depends on the species of
pasture or burning of overgrown or abandoned Trypanosome involved, the mode of transmission,

Vet Lab.indb 179 26/03/2019 10:25