General information

 

Leptospirosis is a bacterial infection caused by Leptospira spp. It is a common disease in many species of domestic animals. Leptospirosis is zoonotic. The bacteria are dispersed by urine of rodents, especially rats. The organism can survive many weeks in a slightly alkaline moist environment. The route of infection is by percutaneous inoculation of wounds or through mucous membranes.

 

Several serovars have been associated with disease. Usually the liver is the target organ of Leptospira sp. Icterus, anemia, weight loss, (ventral) edema and general malaise are the main clinical signs. Ocular involvement (uveitis and hypopyon) may also occur. In elephants only a few clinical cases of leptospirosis have been reported. 

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In one study in Sri Lanka, urine samples from 13 healthy domesticated elephants were collected on three consecutive days and analyzed for leptospiral DNA (Athapattu, 2019). Four elephants (31%) were confirmed to shed pathogenic leptospires in their urine. DNA sequencing followed by phylogenetic distance measurements revealed that all positive elephants were infected with L. interrogans. This study reveals the possibility that elephants may act as a source of infection for humans and recommends that all domesticated elephants that are in close contact with humans be screened to detect leptospiral shedding.

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In a study in India, serum samples were collected from 51 captive elephants kept in three different forest ranges (Shivraj, 2009). The samples were subjected to screening for leptospirosis using the microscopic agglutination test (MAT). It was found that out of the 51 samples seven elephant sera (13.72%) showed antibody titers against two serovars of Leptospira interrogans (L. australis and L. canicola) by MAT indicating the presence of infection or due to the past exposure of captive elephants to leptospiral antigens.

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In Thailand serum from 113 Asian elephants residing in 10 different tourist camps were tested using the microscopic agglutination test against 22 serovars of Leptospira interrogans (Oni, 2007). A seroprevalence of 58 % was found. The prevalent serovars were L. interrogans Sejroe, L. interrogans Tarassovi, L. interrogans Ranarum and L. interrogans  Bataviae and L. interrogans Shermani. These results were similar to studies in domestic livestock and stray dogs in the Bangkok district.

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Because of the potential risk of indirect transmission of Leptospira spp from elephants to humans, 24 environmental samples were collected from an elephant camp area in western Thailand (Chaiwattanarungruengpaisan, 2019). Eighteen samples (75%) were culture-positive for Leptospira spp. The recovered leptospires were mostly derived from water and soil samples from a river and a mud pond, the main areas for recreational activities. The majority of the isolates were classified into the “Pathogens” clade (89%, 16/18) and more than half of the isolates (61%, 11/18) contained species of the “Saprophytes” clade. Notably, two soil isolates from the river beach sampling area were found to contain leptospiral DNA with high similarity to the pathogenic L. interrogans and L. santarosai. The evidence of diverse Leptospira spp., particularly those belonging to the “Pathogens” clade, suggest that the shared environments of an elephant camp can serve as potential infection sources and may pose a risk to the elephant camp tourists and workers. It was not clear from this study whether the elephants were the source of these Leptospira spp. 

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Leptospirosis in elephants

 

One clinical case described the following clinical signs: chronic weight loss (400 kg) over a 4-month period (Fowler, 2006). Anorexia was profound. Leptospirosis was included in the differential diagnosis when the elephant developed uveitis and hypopyon. Titers for multiple serovars of Leptospira reached 1:12,800. The liver was the organ system infected. Icterus was marked. The sclera and hypopyon were both bright yellow. Total bilirubin reached 160 μmol/L (9.4 mg/dl), and liver enzymes were elevated. Ventral edema became pronounced, accompanied by ulcerating lesions of the vulva and various areas of the skin. The tip of the tail necrosed from vasculitis. Blood urea nitrogen and creatinine levels remained normal throughout the course of the disease, indicating that the urinary tract was not involved.

Diagnosis was based on elevated titers for Leptospira serovars plus hypopyon and uveitis. The organism was not isolated nor could antigens be detected by PCR. Two other elephants cohabitating with the ill elephant developed low titers (1:200–400) for Leptospira icterohemorrhagica, but they did not develop clinical disease.

Another case was described by Govindarjan (2006): A 16 yr-old Asian elephant bull was off food for one week. He developed icteric mucous membranes and his urine stained yellow (the author of this report did not mention the color in comparison with the color of normal urine, which is yellow as well). An 8-fold increase of antibodies against L. pyrogenes was observed within a 20-day interval. 

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Diagnosis of leptospirosis is based on serological assays (Micro Agglutination Test MAT, ELISA), PCR, dark field microscopy, and silver impregnation staining.

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Treatment of elephants with clinical leptospirosis consists of the administration of antibiotics (tetracycline, doxycycline). In the case described above by Govindarjan, amoxicillin was given at a dose of 30 g/day IV for 14 days.