Page 202 - The Veterinary Laboratory and Field Manual 3rd Edition

Parasitology 171

bulls. The disease is sexually transmitted so it is invade the wall of the colon, a severe diarrhea can
always important to check the bull for the pres- develop. In severe cases perforation of the colon
ence of Tritrichomonas foetus following a suspected has been reported. In the lumen of the intestine
Tritrichomonas abortion outbreak. Trichomonas some trophozoites will undergo encystations and
gallinae is associated with mouth and crop infec- are passed out in the faeces to infect another host.
tions in song birds and raptors. Recent studies Balantidiosis is common in the Philippines and
confirm the role of Trichomonas blagburni in the other places where there is close contact between
intestinal infections of cats. Control and prevention humans and pigs and where sanitation is poor.
of Tritrichomonas foetus requires testing all bulls
to be used for breeding and possibly changing to Disease prevention
artificial insemination if it is not sure that a bull
is clear following treatment. Treatment with anti- Prevention requires the application of basic sani-
protozoal drugs is effective but must be accompa- tation measures and educating the public about
nied by improved hygiene and husbandry practices. mitigating potential health risks by avoiding
contaminated water and food sources.
Other protozoa

A wide range of other protozoa may cause sig- 3.6 Haemoparasites of ruminants
nificant clinical disease in wildlife, humans and
livestock but these will not be discussed further Haemoprotozoa are of clinical importance world-
here. However, before we go on to consider hae- wide, especially in tropical countries where the
moparasites there is one more enteric protozoan vectors that transmit them may be prolific. The
that will be considered briefly. economic losses due to haemoprotozoal para-
sites in ruminants can be significant with high
mortality in some areas due to diseases such as
balantidiosis East Coast Fever (ECF, Theileria parva). However,
in many cases these diseases are endemic so
Balantidium coli is a cilate parasite found in the local livestock, especially the indigenous breeds,
colon and caecum of pigs, rats and other mam- develop immunity and the consequent losses
mals. It occurs worldwide and is the only member are less dramatic. There is typically a high level
of the ciliate phylum known to be pathogenic of subclinical infection with an associated loss
to humans. Humans can become infected via in production. Two of the most important hae-
the faecal-oral route, usually from the normal moparasites that infect ruminant livestock are
host, the pig, which is usually asymptomatic. Babesia sp. and Theileria sp. These are transmit-
Contaminated water is the most frequent mecha- ted by ticks. Although not strictly ‘parasites’,
nism for transmission. Transmission between Anaplasma sp. and other rickettsia are also dealt
species requires a period of adaptation. Infection with in this section (see Table 3.6b). These
occurs when a host ingests a cyst (that is, via organisms have some similarities with bacteria
water or contaminated food). Once ingested, the and may ‘parasitize’ red blood cells to cause sig-
cyst passes through the digestive system to the nificant clinical disease with red cell destruction
small intestine. Once in the small intestine tro- and the subsequent development of anaemia.
phozoites are produced which colonize the large Anaplasma sp. may be transmitted by ticks as
intestine and feed on intestinal flora. In acute well as by biting flies and mechanical means (for
disease, especially where many trophozoites example, contaminated needles). Many animals

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