IN ANIMALS continued
• There is limited data on Leptospira infection in cats in Australia. A small seroprevalence study showed 0% prevalence in feral cats in south-west Western Australia but as high as 42% in feral cats on Christmas Island, indicating current or prior exposure may be common in some geographic locations. 9 Overseas seroprevalence varies dependent on geography and study population but has been reported as high as 48%. • Shedding occurs via urine, with one study reporting that 8.2% of dogs shed pathogenic leptospires irrespective of health status. 10 A recent study demonstrated cats can shed viable Leptospira spp. organisms. 11
Introduced rats (wild and domestic) are the maintenance host of serovar Copenhageni
CLINICAL DISEASE • In dogs, leptospirosis is classically associated with acute to sub-acute haemorrhagic, renal, or
mitigation. Rodents are a common reservoir host for many serovars. • Leptospires are primarily located in the proximal renal tubules of infected reservoir hosts, however other tissues and organs can also be a source of infection. Reservoir hosts (such as rats) typically do not demonstrate clinical signs but can harbour leptospires in renal tubules for extended periods of time, shedding into the environment via urine. • Urinary shedding may be constant or intermittent, leading to contamination of soil, surface water, streams and rivers. • If the bacteria come into contact with a susceptible animal or person, they can invade (via intact mucous membranes or breaks in the skin), spread through the body and cause generalised infections. PREVALENCE AND RISK FACTORS • An Australian seroprevalence study of shelter dogs in 2008 demonstrated 1.9% of tested dogs were currently, or had previously been infected with Leptospira . 4 State based variation was seen in terms of the prevalence and serovar involved. Seroprevalence was greatest in Victoria (2.8%), Queensland (2.5%) and New South Wales (2.3%). Serovar Copenhageni (in the Icterohaemorrhagiae serogroup) was the most prevalent serovar detected in this study, confirming findings of earlier studies. 5,6 More recently, clinical cases of leptospirosis associated with serovar Copenhageni have been reported in urban dogs in Sydney confirming the importance of this serovar in southern Australia. 7 Infection with serovar Hardjo has also been reported in a dog from Sydney who had visited rural NSW and was involved in herding animals. In north Queensland, serovar Australis is the predominant serovar infecting dogs. 8 • For companion animals the risk of infection is related to exposure to the maintenance hosts (serovar dependent). For example, infection from the serogroup Icterohaemorrhagiae requires dogs to be exposed to rats or areas frequented by rats (e.g. dogs in kennel environments, ratters and pig hunting dogs). There is no published data on the prevalence of Leptospira in rats in Australia.
hepatic disease. Peracute disease has also been reported, associated with death with few preceding clinical signs. Based on seroprevalence data, subclinical infection with leptospires is common. • Overt clinical disease in cats is rarely reported. • Infected animals should be isolated (see recommendations) and treated with IV penicillin derivatives (ampicillin, amoxycillin) until able to accept oral doxycycline. Doxycycline should be given at 5 mg/kg PO q12h for two weeks. In contact household dogs should be tested and treated.
Dogs and humans may be infected from exposure to contaminated water sources
CONTENTS
Companion Animal Zoonoses Guidelines 59
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