The epidemiological relevance of cats in leptospirosis

2019 edition

Andrea Murillo

Leptospirosis is caused by a spirochaete bacterium of the genus Leptospira. Is a zoonotic disease of worldwide distribution that affects a huge diversity of species. In humans, leptospirosis is characterized by nonspecific symptoms such as headaches, high fevers, jaundice, hemorrhagic mucous membranes. When the presentation is severe it can produce multisystemic complications such as acute or hepatic renal failure, or severe pulmonary hemorrhage (P N Levett, 2001) (Bharti et al., 2003). Published data mentions that annually there are more than 500,000 cases of leptospirosis in the world. Most have a severe manifestation, so the mortality is greater than 10% (“WHO, World Health Organization,” 2017). Leptospirosis in humans usually, is acquired from an animal source. The animals involved in leptospirosis are mainly mammals, including aquatic animals. Within this group are rats, horses, cows, pigs, dogs and cats. The main source of excretion of the bacteria is urine. Infection in animals or humans occurs through direct contact with urine or through water contaminated with the bacteria. Infection usually occurs through abrasions, cuts in the skin or conjunctiva (P N Levett, 2001). The presentation of the disease is seasonal, with a maximum incidence in summer and autumn in regions with seasons, where the temperature is a limiting factor in the survival of the leptospires, and in the regions of warm climate during the rains, because otherwise rapid drying would prevent the survival of leptospires (PN Levett, 2001). Even so, its transmission can occur in industrialized countries associated with recreational activities and expeditions in the water; especially stagnant (Pappas, Papadimitriou, Siozopoulou, Christou, & Akritidis, 2008).

As mentioned before, cats are one of the mammals that can spread infected urine to the environment. The clinical relevance of leptospiral infection in cats is still unclear. Is not yet clear how long the shedding of the bacteria by urine in the environment can last. Thus, the role of cats as a route of infection lately gains more attention. Cats could be incidental hosts and reservoirs of the bacteria. To date, very few case reports have been published with a diagnosis of leptospirosis in cats. In cats, clinical presentation is scarce. However, has been shown that cats are susceptible to infection and develop antibodies after infection. The prevalence of antibodies varies according to geographical location in a range of 4% to 37%. Also, shedding of DNA from pathogenic Leptospira species in naturally infected cats was reported with a prevalence ranging from 0% to 67.8%. The infection has been associated with the consumption of infected prey, mainly mice. Therefore, outdoor cats have higher risk.   It is worth highlighting the need to research more thoroughly the role of cats in relation to public health, especially bearing in mind that every day they become more popular as pets.