Page 550 - The Veterinary Laboratory and Field Manual 3rd Edition

Important zoonotic diseases 487

complete. Pigs: Infection often unapparent, pig- Diagnosis: Whole blood, serum, skin biopsy.
lets may show a low-grade encephalitis. Similar Lymph node biopsy. Fixed and fresh tissues from
signs are seen in cases of West Nile virus which dead animals including spleen, bone marrow,
is a related flavivirus. heart blood, liver and lymph nodes for micros-
copy and PCR.
Diagnosis: Serum samples for serology. Tissues
for immunofluorescence or PCR. Also collect Control: Control sandfly vectors (for example,
whole blood and routine post-mortem samples Phlebotomus sp. and others).
so that other diseases can be ruled out. Control:
Control of mosquito vector, monitor sentinel
species, movement control of horses in an out- Leptospirosis
break. Vaccinations are available for humans.
Horses and pigs are vaccinated for JE in parts Cause: Leptospira interogans. There are many
of Asia. serovars of this organism. In cattle, the most
important species are L. hardjo and L. pomona.
In pigs, L. pomona is the main serovar. Other
Leishmaniasis serovars are common in wildlife and most
serovars will infect a range of species.
Cause: Leishmania donovani Epidemiology: The organism is usually spread
in infected urine with consequent contamina-
Epidemiology: This is a protozoal parasite which
is transmitted by a sandfly vector or by direct tion of water and pasture. Large numbers of
contact with an infected animal. There are organisms may be passed in abortion fluid. The
various subspecies. L. donovani donovani causes organism can gain entry through mucous mem-
epidemic leishmaniasis in humans and is princi- branes including the conjunctiva. On farms pigs
pally a human disease but L. donovani infantum is are often an important source of leptospirosis
transmitted by the sandfly to dogs and jackals. in cattle. Urine from infected rats and other
Humans may become infected by direct contact. rodents can contaminate human drinking water.
Both of these forms (Visceral leishmaniasis) Signs in animals: There may be abortion in preg-
cause weight loss, malaise, lymphadenopathy nant livestock or silent infections in juveniles
and anaemia in humans. Cutaneous leishmani- depending on the serovar involved. Cows which
asis is caused by Leishmania tropica minor (human abort may develop red milk. Leptospira pomona
reservoir) and other species (rodent reservoirs) can cause haemolytic anaemia and haemoglobin-
and is transmitted by the sandfly in urban and uria in calves. Leptospirosis in dogs may result
rural areas respectively. In this form of the dis- in systemic disease with fever, haemolytic anae-
ease the main lesion is a small un-healing ulcer. mia and jaundice.
Signs in animals: Dogs may develop the cutane- Diagnosis: Serum (paired samples preferably
ous and visceral forms of the disease and can, taken 2–4 weeks apart), urine (fresh and fixed in
along with rodents, be a source of infection for formalin), foetal stomach contents and samples
humans. The skin lesions may be focal or spread of placenta from abortion cases, fresh and fixed
as a crusty area with hair loss. The disease may tissues from dead animals. Whole blood and
progress to a wasting form with generalized milk. Microscopy and culture where possible.
lymphadenopathy, anaemia, enlarged spleen and Molecular methods can also be used to identify
terminally, death. Treatment may be difficult. Leptospires.

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