Discussion
The main source of parasitic infection in zoo animals is not well known. At the Ljubljana Zoo, as in other European zoos, feeding carnivores with raw meat that is potentially infected with T. gondii tissue cysts is a common practice. Infected felids can spread T. gondiioocysts in their environment and thus contaminate food, bedding, and water. In some zoo felids (Otocolobus manul ), toxoplasmosis with a fatal outcome has been reported (Bartova 2014). Carnivores can also be infected by hunting some small prey species with free access to the zoo, such as small wild rodents and birds. Another source of infection might be the presence of feral cats in the zoo, which can spread oocysts in their feces to zoo enclosures. In our study, T. gondii was detected by PCR in tissues of four wild rodents and in one laboratory mouse that died. The laboratory mouse came from a specific pathogen-free breeding compound; the route of infection of this animal remains unknown. One possibility is food contaminated with sporulated T. gondii oocysts due to improper storage of prepared pellets.
Fatal toxoplasmosis was described in six tammar wallabies (Macropus eugenii ) in the Budapest Zoo and Botanical Garden between 2006 and 2010 (Sós, 2012). Wallabies are known to be susceptible to T. gondii infection, and feral cats are suggested as the main source of the parasite in the zoo environment. In our study, a high prevalence of T. gondii was found in Camelids and Diprotodontia, which could be related to contamination of food such as hay or of substrate material in their enclosures, which is mostly sand. A high risk of contamination of this substrate with the feces of feral cats as well as difficulties in keeping stray cats outside the zoo (it is located in the city) increase the possibility of infection withT. gondii oocysts. New World Primates are highly susceptible to clinical toxoplasmosis, and the infection is often fatal with various pathological manifestations (Epiphanio, 2003). High prevalence was previously recorded in primates such as the red-faced spider monkey (Ateles paniscus ) and tufted capuchin (Cebus apella ) from a zoo in Brazil, at 67% (Minervino, 2010), and in a Barbary macaque (M. sylvanus ), gorilla (Gorilla gorilla ), chimpanzee (Pan troglodytes ), and orangutan (Pongo pygmaeus ) in the Czech Republic, at 45% (Sedlák, 2006). In our study, T. gondiiantibodies were found in 25% of primates (chimpanzee, Pan troglodytes ). Ingestion of sporulated T. gondii oocysts in contaminated feed is presumed to be the main source of infection. Carefully washing vegetables and fruits as well as regularly cleaning the kitchen may reduce the risk of infection in this group of animals. Toxoplasmosis has been recorded in zoo birds; for example, in canaries and black-winged lories (Eos cyanogenia ) (Weiss, 2011). In our study, antibodies to T. gondii were not found in any of the birds tested; however, two mute swans died and T. gondii was detected in their tissue by PCR. These samples were genotyped and characterized as type II, which is known to be highly predominant in humans and animals in Europe and North America (Costache, 2013; de Sousa, 2006). Water contaminated with T. gondii oocysts is one possible source of the infection in this case.
E. cuniculi is a very important parasite of rabbits throughout Europe (Jordan, 2006). This is in accordance with results from our study because we found the highest prevalence of E. cuniculi antibodies in Lagomorpha (83%) in European rabbits (Oryctolagus cuniculus ). Placentitis, premature birth, and perinatal death has been described in connection with E. cuniculi infection in an alpaca (Vicugna pacos ) (Webster, 2008). In our study, a high prevalence of E. cuniculi antibodies was found in Bovidae (81%) and Camelidae (67%). Antibodies to E. cuniculi were found in an alpaca (Vicugna pacos ) and a guanaco (Lama guanicoe ). One E. cuniculi –seropositive alpaca died, but the parasite was not detected by PCR in its tissue.
Clinical disease and positive isolation of E. cuniculi was reported in captive emperor tamarins (Saguinus imperator ) and cotton-top tamarins (Saguinus oedipus ), which seem to be highly susceptible to infection (Guscetti 2003; Juan-Sales 2006). In our study, chimpanzees, lemurs, and gibbons were negative. Herbivores had a higher chance of being infected compared to carnivores, which could suggest the presence of E. cuniculi spores in the environment as a main source of infection. E. cuniculi infection in birds has no clinical importance, but some avian species could serve as reservoirs for these microsporidia (Hinney, 2016). In our study, antibodies toE. cuniculi were found in mute swans and helmeted guineafowls (Numida meleagris ).
Chlamydia abortus and Coxiella burnetii are pathogens that are well known to cause abortions as well as various health problems in zoo animals (Lloyd, 2010). The negative results obtained in our study may be due to limited exposure, good preventive veterinary care, and suitable disinfection plans.
Zoos are institutions open to the public. A large variety of different animal species usually with a high density of animals, open enclosures, the presence of stray cats and wild rodents, and close contact with people are important factors for transmission of diseases, often with anthropo-zoonotic potential, which raises public health concerns. Therefore, monitoring transmissible diseases in zoo animals and understanding their dynamics is of great importance and is an inseparable part of preventive health care in zoological collections.
Financial support: The study was supported by internal grant of VFU Brno (FVHE/Literák/ITA2019).