Zoos emphasize animal hygiene and public health countermeasures for good health management of captive animals. The target agents include pathogens infective to both zoo animals and livestock, wildlife, or humans. There is no complete border between on a zoo ground and natural environment. Therefore zoo biosecurity countermeasures including prevention from infectious diseases outside and preventive medicine protocols are practiced every day by zoo veterinarians and animal-keepers. For example, mosquito surveillance and control is common practice in most North American zoos since the introduction of West Nile virus. On the other hand, infectious diseases of captive animals should be prevented to spread out in natural environment. Investigation of injured wildlife and necropsies of the carcasses found on zoo grounds must be useful monitoring tools of wildlife diseases, and provide a baseline measure of the risk posed by local wildlife. Moreover these approaches should be part of the basic preventive medicine protocols where feasible at zoos. Actually, there is a case of Eurasian Tree Sparrow (Passer montanus) mortality in Hokkaido, winter 2008–2009, including an initial case found dead on a zoo ground, which was revealed caused by an epidemic infection with Salmonella Typhimurium. The initial case was diagnosed with salmonellosis by pathological examination for a preventive medicine program by a zoo veterinarian. Zoos can play an important role as a wildlife conservation center in monitoring and managing ecological health, which is supporting lives of humans, livestock, and wildlife, based on conservation medicine by conducting biosecurity countermeasures and monitoring of infectious diseases in wildlife.
Zoological gardens keep many kind of endangered wildlife outside its natural habitat for species survival and future reintroduction and breed them intentionally under keeping genetic diversity. Zoological gardens build international network to effectuate these activity so-called ex situ conservation. Control of infectious disease is large issue when wild animals in captivity are moved internationally. Animal health requirements of wildlife import for each species have been established by animal health authority of each country, Legal quarantine are conducted by animal quarantine service of ministry of agriculture, forestry and fisheries when zoo import these wildlife from abroad, based on the act on prevention of infectious diseases and medical care for patients suffering infectious diseases, the act on domestic animal infectious diseases control, rabies prevention act. For example, it is necessary for primates to legal quarantine at export country and import country for 30 days each, intended for Ebola hemorrhagic fever and Marburg disease, based on the act on prevention of infectious diseases and medical care for patients suffering infectious diseases. But there are few zoo facilities where legal quarantine can be performed in Japan. Legal quarantine may often become a barrier to effectuate ex situ conservation under the international cooperation. It is necessary to prepare the quarantine facility fit for zoo animals and to revise the laws to suppose to ex situ conservation at the zoological gardens.
Treatment of infectious diseases and management of infected animals is easier in a zoo, because it is easier to detect infectious diseases and understand the prevalence of pathogens and disease occurrence pattern. On the other hand, because many species of animals are housed in a sympatric environment in a zoo, there is direct and/or indirect contact of the animal species that would normally never occur in nature. This arrangement provides a new host for the pathogen. Differences in the sensitivity of various animals to pathogens may be the cause of an epidemic of infectious disease. Inappropriate habitat is one of the factors responsible for infection. Moreover, an increase in the population density of animals results in massive exposure to and propagation of pathogens. Further, occurrence of infectious diseases may also occur because of ingestion of contaminated feed. Herein, we discuss “infectious disease in zoo” by presenting several cases.
Zoos and aquariums are keeping various species in a variety of ways and facilities for ex-situ conservation, education, research and other purposes. Since a wide range of species are kept, there is the possibility for outbreaks of a number of different infectious diseases. In addition, these institutions are open to the general public, and a huge number of people are visiting there every year. Therefore it is not easy to protect the captive animals from every infectious disease. In recent years severe infectious diseases occur frequently, control of infectious diseases is becoming more important in zoos and aquariums. To control infectious diseases, it is necessary to take preventive measures against the occurrence and spread of diseases in systematic and well-planned ways. To prevent the occurrence of infectious diseases, improvement of immunity through daily health maintenance and vaccination, and break of infection routes through cleansing of captive environment and setting up the physical barriers against pathogens are effective. To prevent the spread of diseases, early detection through quarantine, regular physical examination and necropsy, and containment of pathogens through movement restrictions, isolation, treatment and culling of captive animals can be appropriate measures. In order to increase the effectiveness of these measures, providing the systematic responses such as preparing the manuals and stockpiling of necessary supplies are required. As long as animals are kept for purpose of ex-situ conservation or education, it is impossible for the captive animals to completely cut off all the contacts with the pathogens, so that it is difficult to eliminate the infections. Therefore it would be important to consider how to reduce the risks on the basis that infectious diseases can be occurred.
In recent years, zoonotic infectious diseases such as highly pathogenic avian influenza and foot-and-mouth disease have been being spread around the world, and some are suspected to have a relationship with wild animals. It is needed to build wildlife disease information networks, conduct fundamental survey research through international collaboration on the implementation of an early warning system for the occurrence of infectious diseases common in wildlife and to work on the risks of diseases transmitted by wildlife. To build a surveillance system aiming to prevent and control wildlife infectious diseases will be socially desirable, but there are several economic and social concerns including the low representation of veterinary professionals in this field. I’d therefore like to propose the network system for prevent and control wildlife infectious diseases using by international zoo network and collaboration with zoo veterinary resources. Combining the human network with veterinary medical science among zoos of the world, early warning system for domestic and wildlife infectious diseases will be formulated and systematic protection against zoonoses for the future. It can eventually contribute to the maintenance of animal health, human health and ecosystem health based on conservation medicine.
The Eurasian river otter Lutra lutra is the most widely distributed otter species. The European subspecies L. lutra lutra (Linnaeus, 1758) kept in European zoos has four strains; two of which (the A- and B-lines) have been introduced into zoos and aquariums in Japan. As the genetic backgrounds of, and differences between, these two strains were unknown, we identified partial nucleotide sequences (307bp) of the mitochondrial cytochrome b gene from an A-line and a B-line individual, A-line cyb and B-line cyb, respectively, kept in an aquarium in Japan. The nucleotide sequence of the A-line cyb and B-line cyb showed 98.7% identity and are distinguishable by the restriction fragment length polymorphism analysis. A-line cyb was 100% identical to the cytochrome b of L. lutra lutra, whereas B-line cyb failed to show 100% identity to the known nucleotide sequences on the database. The phylogenetic analysis of our sequences with those from a previous study revealed that the two strains had already been introduced into Japan by at latest the 1990s. These results suggest that there are slight differences between the A- and B-line individuals used in the present study. However, further investigations, including re-evaluation of the taxonomy of L. lutra subspecies, are needed to clarify the differences between the two strains.