Page 209 - The Veterinary Laboratory and Field Manual 3rd Edition

178 Susan C. Cork and Mani Lejeune

subclinical disease. In warm humid regions and brain crush smears should all be taken. If
Babesia bovis and B. bigemina are the common- rabies is suspected the brain should also be sent
est species. In cool damp countries, B. divergens to a laboratory equipped for rabies diagnosis.
and B. major predominate. Babesia sp. proto- Ante-mortem diagnosis can be confirmed by
zoa are transmitted by various species of ticks clinical signs along with blood smears which
such as Rhipicephalus (Boophilus) sp., Ixodes sp., show Babesia sp. organisms in red blood cells.
Haemaphysalis sp. and Dermacentor sp. Unlike the Thick and thin smears should be made and
tick cycle of Theileria sp., adult ticks transmit stained with Giemsa. Immunological tests may
some Babesia sp. in the eggs to their progeny also be used to diagnose infection, the most
(transovarian transmission) and therefore may frequently used tests being the complement fixa-
reinfect new hosts from generation to generation. tion test (CFT), fluorescent antibody tests (FAT)
Mechanical transmission through contaminated and the gel precipitation test (GPT). For details
instruments and needles is also possible. see Chapter 6. In areas where laboratory services
are not available an animal health officer may try
cLInIcaL SIGnS and dIaGnoSIS ‘response to treatment’ to distinguish Babesiosis
The typical clinical signs include a high tempera- from other haemoparasitic diseases. Babesia sp.
ture (41ºC/106°F) usually 8–17 days after the are readily killed by a number of drugs (for
bite of an infected tick, this may be associated example, Diminazene, Imidocarb) and this helps
with sudden loss of appetite. Anaemia (mucous to differentiate the disease from others such as
membranes become pale and later may become anaplasmosis.
yellow) develops as the course of the disease
continues and some animals develop nervous Anaplasmosis – gall sickness
signs (may be confused with rabies). Animals
tend to become weak as the anaemia becomes This is a disease caused by rickettsial organ-
more pronounced and the urine is often reddish isms of the genus Anaplasma. It was previously
or brown in colour, hence the name ‘red water thought to be a protozoan and is often described
fever’. After 2–3 days untreated animals may die along with other haemoparasitic diseases. The
or the disease may become chronic with meta- organism is seen in the red blood cells on
bolic disturbance and eventual death. In chronic infected mammals and is transmitted by tick
babesiosis the animal appears dull, emaciated vectors. Anaplasma sp. are found worldwide
and has a poor coat. Diagnosis can be confirmed both in tropical and temperate areas. The main
at necropsy although the post mortem signs species of veterinary importance are Anaplasma
can be confused with Theileriosis. The spleen marginale, which causes significant clinical dis-
is characteristically swollen and the carcass is ease, and A. centrale, which is usually associated
anaemic, sometimes yellowish (jaundiced). with a milder form of disease. The incubation
The bladder contains red or pink urine. The period for the development of clinical anaplas-
kidneys are enlarged and congested and there mosis is variable and can range from several
may be haemorrhages in the heart, stomach and days to 5 weeks (usually 30–40 days). The
intestine. In areas where tick borne diseases are source of infection is usually ticks (Dermacentor
common more than one type of blood parasite sp., Rhipicephalus sp. and others) which have fed
may be present in blood smears but some may on sick or convalescent cattle, asymptomatic
not be very pathogenic. To check for the pres- carriers or possibly, infected wild ruminants.
ence of Babesia sp. and other blood parasites, Horse flies (Tabanidae), stable flies (Stomoxys
samples of blood, lymph nodes, spleen smears sp.) and other biting insects can also transmit

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