IN ANIMALS continued
HOST ADAPTED CYCLE
Spillover infection of humans may occur through direct or indirect exposure to urine from a reservoir host, or less commonly due to exposure to urine from another infected incidental host
INCIDENTAL CYCLE
DIAGNOSIS • Diagnosis may be based on identifying leptospires in body fluids, with PCR the primary modality. Serology may also be used for diagnosis. A single microscopic agglutination test (MAT) titre >1:800 is considered positive against non-vaccine serovars. Demonstration of seroconversion with a fourfold or greater increase in titre between samples taken 2 to 4 weeks apart is also considered diagnostic. Serology (MAT) is required to identify the infecting serovar. • Infection results in an acute leptospiraemia lasting 7-10 days, followed by renal colonisation and leptospiruria, thus appropriate samples should be tested. 2 As the time of infection
is typically unknown, simultaneous testing of blood and urine is recommended to increase diagnostic sensitivity. PREVENTION • Vaccination of dogs is possible, however immunity engendered by leptospirosis vaccines is serovar, or at best serogroup specific. In Australia, a registered vaccine is available against serovar Copenhageni and an unregistered vaccine against serovar Australis is available on conditional permit (available for dogs in Queensland and Northern Territory and for military/customs dogs in all states). Leptospira vaccines do not provide sterilising immunity but may reduce shedding. 3
TRANSMISSION
• Leptospires are excreted constantly or intermittently in urine of infected carrier animals resulting in contamination of soil, surface water, streams and rivers. • Organisms do not replicate outside the host, but may survive for prolonged periods. Environmental survival of leptospires is favoured by warm moist conditions, and may exceed 20 months in nutrient poor water. 12 Leptospires are susceptible to desiccation and UV light. Human and animal outbreaks have been linked to increased rainfall, flooding or contact with stagnant or slow-moving water. • Leptospires gain entry to the body through skin abrasions (e.g. wounds and scratches) or across mucous membranes, including those of the gastrointestinal (via ingestion), respiratory (via inhalation) or genital tracts (via sexual transmission – very rarely in humans) and conjunctiva of the eyes. • Therefore transmission is possible through direct contact with urine from infected animals or indirect contact with water, soil or food contaminated with urine containing leptospires.
CONTENTS
60 Companion Animal Zoonoses Guidelines
Made with FlippingBook - professional solution for displaying marketing and sales documents online