RESUMEN
A massive outbreak of anthrax in the wildlife of the Malilangwe Wildlife Reserve in Zimbabwe between August and November 2004 resulted in the death of almost all the reserve's estimated 500 kudu (Tragelaphus strepsiceros). Other species badly affected were nyala (Tragelaphus angasi), bushbuck (Tragelaphus scriptus), waterbuck (Kobus ellipsiprymnus) and roan antelope (Hippotragus equinus), which suffered losses of approximately 68 per cent, 48 per cent, 44 per cent and 42 per cent of their populations, respectively. Buffalo (Syncerus caffer) were also badly affected and although their population suffered only a 6 per cent loss, the numbers of deaths ranked second highest after kudu. To the authors' knowledge, this is the first record of anthrax in wildlife in Zimbabwe.
Asunto(s)
Antílopes , Carbunco/veterinaria , Brotes de Enfermedades/veterinaria , Rumiantes , Animales , Animales Salvajes , Carbunco/epidemiología , Carbunco/prevención & control , Vacunas contra el Carbunco/administración & dosificación , Bacillus anthracis/inmunología , Femenino , Masculino , Estaciones del Año , Vacunación/veterinaria , Zimbabwe/epidemiologíaRESUMEN
Institution of a policy of vaccination in endangered species with a vaccine not previously administered to it cannot be undertaken lightly. This applies even more in the case of cheetah (Acinonyx jubatus) with their unusually monomorphic gene pool and the potential restrictions this places on their immune responses. However, the recently observed mortalities from anthrax in these animals in the Etosha National Park, Namibia, made it imperative to evaluate vaccination. Black rhinoceros (Diceros bicornis), another endangered species in the park, have been vaccinated for over three decades but the effectiveness of this has never been evaluated. Passive protection tests in A/J mice using sera from 12 cheetahs together with enzyme immunoassay indicated that cheetah are able to mount seemingly normal primary and secondary humoral immune responses to the Sterne 34F2 live spore livestock vaccine. Overall protection rates in mice injected with the sera rose and fell in concert with rises and declines in antibody titres, although fine analysis showed that the correlation between titre and protection was complex. Once a high level of protection (96% of mice 1 month after a second booster in the cheetahs) had been achieved, the duration of substantial protection appeared good (60% of the mice 5 months after the second booster). Protection conferred on mice by sera from three of four vaccinated rhino was almost complete, but, obscurely, none of the mice receiving serum from the fourth rhino were protected. Sera from three park lions with naturally acquired high antibody titres, included as controls, also conferred high levels of protection. For the purposes of wildlife management, the conclusions were that vaccination of cheetah with the standard animal anthrax vaccine causes no observable ill effect in the animals and does appear to confer protective immunity. At least one well-separated booster does appear to be desirable. Vaccination of rhino also appears to be justified from the limited data obtained.
Asunto(s)
Acinonyx/inmunología , Vacunas contra el Carbunco/uso terapéutico , Carbunco/prevención & control , Carbunco/veterinaria , Artiodáctilos/inmunología , Animales , Vacunas contra el Carbunco/efectos adversos , Anticuerpos Antibacterianos/análisis , Anticuerpos Antibacterianos/biosíntesis , Anticuerpos Antibacterianos/uso terapéutico , Ensayo de Inmunoadsorción Enzimática , Femenino , Inmunización Pasiva , Masculino , RatonesRESUMEN
Tests for airborne movement of anthrax spores downwind from three heavily contaminated carcass sites were carried out under a range of wind conditions. Anthrax spores were detected in just three of 43 cyclone or gelatin filter air samples taken at distances of 6, 12 and 18 m from the sites. In addition, nine positives resulted during sampling sessions in which the site was mechanically disturbed, with a further five positives being found in sessions subsequent to those in which the site had been disturbed. The three positive samples not related to man-made disturbance were associated with the highest winds experienced during the study. Despite colony counts exceeding 100 on the culture plates in three instances, calculations showed that these represented very low worst case probable spore inhalation rates for animals or humans exposed to such levels. The low number of positives, the clear pattern of rapidly declining numbers of anthrax spores with distance downwind from the centres of the sites apparent on settle plates, and the persisting levels of contamination despite wind and rain, collectively suggest that the anthrax spores were associated with fairly heavy particles, although this was not seen by electron microscopy on soil samples from the sites. Overall, the findings are interpreted as indicating that it is very unlikely that Etosha animals contract anthrax by the inhalation route while simply in transit near or across a carcass site. The significance of the observations in relation to weather conditions in the Etosha, other studies on particulate aerosols in the region, and reports of long-distance airborne movement of microbes, is discussed.
Asunto(s)
Microbiología del Aire , Carbunco/microbiología , Bacillus anthracis/aislamiento & purificación , Esporas Bacterianas/aislamiento & purificación , Animales , Técnicas Bacteriológicas , Equidae/microbiología , Microscopía Electrónica de Rastreo , Namibia , Microbiología del SueloRESUMEN
Analysis of mortality records has revealed distinct patterns in the incidence of anthrax in elephant and plains ungulates. The seasonal peak among the former is in November at the end of the dry season, while among the latter it occurs in March towards the end of the rainy season. Among elephants, there has been a notable spread of the disease to the west of the Park. Age and sex analyses indicate that, except for zebra, proportionally greater numbers of adult males die of anthrax among the species predominantly affected; however, zebra carcases are difficult to sex. In a study to identify possible environmental sources of infection, B. anthracis was detected in 3.3% of 92 water and 3.0% of 230 soil samples collected at different times of the year from 23 sites not associated with known cases of anthrax. Slight seasonal differences were noted with 5.7% positives occurring in the cold-dry period (May to August), 3.5% in the hot-dry season (September to December) and 1.4% in the hot-wet season (January to April). Higher rates (26.0% of 73 samples) were found in water from waterholes in the western part of the Park at the time of an outbreak in elephants. The possible importance of scavenger faeces was confirmed with > 50% of vulture, jackal and hyaena faeces collected from the vicinity of confirmed anthrax carcases yielding B. anthracis, sometimes in substantial numbers, while no spores were found in faeces not associated with known anthrax carcases. Despite terminal B. anthracis levels of usually > 10(7) cfu/milliliters in the blood of animals dying of anthrax, spore levels in soil contaminated by such blood at sites of anthrax carcases ranged from undetectable to a few tens of thousands. The rapid loss of viability in soil and water of anthrax bacilli was monitored experimentally and the importance of soil type demonstrated. Survival and extent of sporulation of the bacilli in water were shown to be dependent on the rate at which the blood was diluted out. Other relevant parameters examined were background flora, pH and sunlight.
Asunto(s)
Carbunco/epidemiología , Carbunco/veterinaria , Bacillus anthracis/aislamiento & purificación , Animales , Animales Salvajes/microbiología , Carbunco/microbiología , Bacillus anthracis/efectos de la radiación , Heces/microbiología , Femenino , Incidencia , Masculino , Namibia , Estaciones del Año , Microbiología del Suelo , Luz Solar , Rayos Ultravioleta , Microbiología del AguaRESUMEN
Results are presented from a number of epidemiological studies using enzyme immunoassays (EIA) based on the purified anthrax toxin antigens, protective antigen, lethal factor and oedema factor. Studies on sera from a group of 62 human anthrax patients in Turkey and from cattle in Britain following two unrelated outbreaks of anthrax show that EIA using protective antigen can be a useful diagnostic aid and will detect subclinical infections in appropriate circumstances. A serological survey on wildlife in the Etosha National Park, Namibia, where anthrax is endemic, showed that naturally acquired anthrax-specific antibodies are rare in herbivores but common in carnivores; in carnivores, titres appear to reflect the prevalence of anthrax in their ranges. Problems, as yet unresolved, were encountered in studies on sera from pigs following an outbreak of anthrax on a farm in Wales. Clinical details, including treatment, of the human and one of the bovine outbreaks are summarized and discussed in relation to the serological findings.