By Christof Schenck and Elke Stail', Frankfart Zoological Society, Alfred-Brehm-Platz 16, 60316 Frankfurt, and use Storch, Munich Wildlife Society, Linderhof 2, 82488 Ettal, Germany.

Diseases of domestic animals which spread to contiguous wild populations may cause serious mortality. Bovine tuberculosis, which is believed to have spread from adjacent domestic cattle in the 1960s, has infected over half the Cape buffalo (Syncerus Coffer) in the Kruger National Park, South Africa (Bengis et al, 1996). In 1985, the last remnant of the black-footed ferret (Mustela nigripes) population in North America was reduced from an estimated 58 individuals in 1985 to 16 individuals in 1986 (Williams et al, 1988). This catastrophic decline in numbers was attributed partly to infection by canine distemper virus (CDV) and partly to losses during juvenile dispersal. CDV typically causes disease in domestic dogs. In Tanzania, CDV has caused the death of lions (Felis Len) and other wild carnivores (Roelke-Parker, 1996) and is believed to have been transmitted to the wildlife by infected domestic dogs owned by local tribesmen.

Settlers and Indian tribes along the Manu River and in the Manu National Park (MNP) in southeastern Peru, keep domestic chickens, pigs, cats and dogs. The presence of these domestic animals may expose the local wildlife to diseases such as canine distemper (CD) and canine parvovirus disease (COD). Domestic animal diseases have been discussed as potential causes of the population crashes of the canids Speothos venaticus and Atelocyous microtis and of peccaries (Tayassu pecari) in MNP (Terborgh, pers. Come.).

MNP supports an important population of the endangered mustelid, the giant Peruvian otter. Mustelids are susceptible to lethal infection with CDV (Rogoshik & Brandes, 1991). Since Peruvian giant otters are large mustelids they are probably susceptible to CDV and it is possible that this virus has been responsible for the extinction of the giant otter populations elsewhere in the Amazon Basin. In some places giant otters live in close proximity to human settlements. CDV does not live long outside the animal body but can survive for up to 14 hours, even when exposed to bright sunlight, (Suter, 1989). Thus, contact with faeces from an infected dog could well provide a source of infection for the giant otters and other susceptible wildlife. Dispersing giant otters, locally known as "solitaries", may travel long distances (Staib, 1996) and so could carry CDV to distant, immunologically naive populations. For example, in April 1991 we observed an individual otter, a native of Cocha Otorongo, close to the village of Boca Manu, at the edge of MNP. In October, he had traveled back to Otorongo, 81 kms upstream of Boca Manu.

Our concern for the potential risk to the Manu giant otter population became more serious when, at the end of 1990, a lethal epizootic of unknown origin was observed to affect the domestic dogs along the Madre de Dios river, from Atalaya to Boca Manu, at the edge of MNP. The disease was restricted to dogs and according to the local people it killed "almost all" the dogs in the region. Also, in previous years, similar epizootics were said to have occurred in the village dogs. At about this time we learned that juvenile giant otters were reported to have died of CPV infection in Hagenbeck Zoo in Germany (Wunnemann, pers. Coma.). CPV infection has only been recognized since 1978. CPV infection occurs by contact with infected animals or their excretions, as does infection with CDV, but CPV is much more resistant in the environment and can remain infective for up to six months (Suter, 1989).

In order to investigate the distribution and abundance of the two domestic animal diseases that may infect giant otters, canine distemper and canine parvovirus, in August 1995 we collected blood samples from 16 dogs in Indian and settler villages in the core area and cultural zone of MNP (Fig.1). The sampled dogs were all estimated to be under four years old. Immediately after sampling, several mls of blood were transferred to 'monovettes with serum-jelly, to separate the serum. About two hours later the serum was transferred to fresh tubes by pipette. Each serum sample was then divided into two: 1 ml was kept as cool as possible (< 30 C) without preservatives and 1 ml was added to 100 I Na-Azid 1.0k for preservation. Four weeks later, the samples were analyzed at the Labor fur Klinische Diagnostik, Labokin, Bad Kissingin, Germany.
 

Somewhat surprisingly, all samples, including those not treated with preservatives, were considered suitable for analysis by the laboratory (Table 1). According to Labokin (and also to Professor Max Appel, of Cornell University) to whom the results were submitted for comment, CDV titres of 1:20 or less and CPV titres of 1:50 or less probably indicate that these dogs had not been exposed to virulent infection. With regard to CPV, 5/16 dogs showed high titres indicating recent infection, whereas the remainder (11/16), which had titres of 1:50 or less were probably carrying maternal antibodies. With regard to CDV, the one dog, (which could have been over 4 years old), clearly had been infected and in that case, could have been a survivor of the 1990-1991 die-off while the remainder, all with low, insignificant titres, were too young to have been infected at that time. These results show that both CDV and CPV have been present in the domestic dogs of the villages where they were sampled.
 

CPV occurs all over the world and antibodies may be found in the sera of 80% of middle-aged dogs. The canine strain of the disease is largely host-specific for canids, wild and domestic, and causes disease mainly in pups and juveniles. After surviving infection with CPV a dog is immune, probably for life. CPV was thus thought to be a minor risk to the giant otters. However, the reported death of young giant otters, ascribed to CPV, in Hagenbeck Zoo in Germany, and the presence of CPV antibodies in the dogs of the Manu area may indicate that a risk remains for the giant otters of MNP. In contrast with CPV, the virus of CD cannot survive in small host populations. The negative results from the inner Manu indicate that the region was at least temporarily free from CDV. The results from the outer Manu show that CDV infection must have occurred at some time previously. The clinical signs shown by the infected dogs, the epizootic nature of the disease and the deaths of dogs of all age classes, all indicate that the die-off of 1990-1991 was probably due to canine distemper. The life-span of domestic dogs in the Indian and settler villages of MNP is believed to be short. Poor nutrition, high parasite loads, enzootic CPV and frequent accidental deaths due to snake bite etc. all tend to keep the dog population relatively low. However, itinerant dealers regularly sell puppies from distant urban areas to the rain-forest villagers and this, of course, presents a high risk of the introduction of CDV and CPV into immunologically naive rural dog populations.

Among the wild carnivores of MNP, giant otters could be particularly threatened by domestic animal diseases such as CPV and CDV. They are inhabitants of the lakes and rivers, habitats which are often frequented by humans and their dogs. They live in social groups and they disperse over long distances. Their natural parasite load (Schenck, 1996) and the anthropogenic mercury contamination of their food (Gutleb et al, 1993) may compromise their immune systems and

A solution to this problem might be to immunize the dealers puppies against CDV and CPV, before they reach the rain-forest villages. But this would be expensive, very difficult to implement and would need to be maintained for the foreseeable future. It might also result in the survival of many more dogs, which could present more environmental problems in the rain-forest. We feel that the giant otters of Manu National Park must remain at what is a theoretical risk for the moment, at least until that risk can be further quantified and the susceptibility of the otters to the canine diseases can be confirmed. However, we recommend that in order to minimize the risk of the giant otters being exposed to canine diseases, the MNP authorities should limit the number of dogs that are allowed to enter the Park. At the same time they should monitor the giant otter populations (and the domestic dogs, too) for evidence of epizootic diseases, both inside the MNP and in the surrounding areas.