IN ANIMALS continued
a
b
Coproscopy can be used to diagnose Giardia infections: (a) unstained and (b) stained (Lugol’s iodine) preparations
DIAGNOSIS • Several diagnostic assays are available for Giardia , including coproscopic identification of cysts using zinc
of Giardia by dogs in Indigenous communities have been found in many studies. The canine and feline adapted assemblages predominate in Australian studies, although the potentially zoonotic G. duodenali s (Assemblage A) has been identified in dogs. 15 • Prevalence and cyst shedding intensities are higher in younger animals, those from high population density environments (shelters, kennels, catteries) and in those with compatible clinical signs (see below). 4,5 CLINICAL DISEASE • Infection is usually subclinical. 4,5 Clinical signs are more likely to occur in young or immunosuppressed animals, or those with concurrent gastrointestinal pathogens or parasites. Chronic mucoid diarrhoea and weight loss are the most common findings. Systemic signs of illness are uncommon.
sulfate centrifugal flotation, point-of-care coproantigen tests, and molecular diagnosis using real-time PCR. In a comparative study, real-time PCR has been demonstrated to have the highest sensitivity (97.0%), followed by coproantigen detection (71.9%), with standard coproscopy having the lowest sensitivity (48.2%). 16 • Determination of assemblage/species, and therefore zoonotic potential, is not routinely performed by diagnostic laboratories. In the absence of this information all animals testing positive should be considered as carrying potentially zoonotic species and appropriate precautions taken. • It is not recommended to treat clinically well animals that test positive for Giardia .
TRANSMISSION
• Giardia is transmitted via the faecal-oral route through the ingestion of cysts, either directly through close contact, or through contaminated food and water. • Contaminated or untreated water is a risk for infection, such as at camping sites, rivers and lakes. • Cysts can survive in the environment for prolonged periods under moist, cool conditions, but are susceptible to desiccation in hotter, dryer environments. • Giardiasis has a low infectious dose with ingestion of as little as ten cysts capable of causing infection. 17
CONTENTS
46 Companion Animal Zoonoses Guidelines
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