Lindeque P M, Turnbull P C
Etosha Ecological Institute, Namibia.
Onderstepoort J Vet Res. 1994 Mar;61(1):71-83.
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.
对死亡记录的分析揭示了大象和草原有蹄类动物中炭疽发病率的明显模式。前者的季节性高峰出现在旱季末的11月，而后者则出现在雨季末的3月。在大象中，该病已显著蔓延至公园西部。年龄和性别分析表明，在主要受影响的物种中，除了斑马，成年雄性死于炭疽的比例相对更高；然而，斑马尸体难以辨别性别。在一项确定可能的环境感染源的研究中，从与已知炭疽病例无关的23个地点在一年中的不同时间采集的92份水样和230份土壤样本中，分别有3.3%和3.0%检测出炭疽杆菌。注意到有轻微的季节性差异，冷干期（5月至8月）阳性率为5.7%，热干季（9月至12月）为3.5%，热湿季（1月至4月）为1.4%。在大象爆发疫情时，公园西部水坑的水样中发现了更高的阳性率（73份样本中的26.0%）。食腐动物粪便的潜在重要性得到了证实，从确诊炭疽尸体附近收集的秃鹫、豺和鬣狗粪便中，超过50%检测出炭疽杆菌，有时数量可观，而在与已知炭疽尸体无关的粪便中未发现孢子。尽管死于炭疽的动物血液中炭疽杆菌的终末水平通常>10⁷cfu/毫升，但在炭疽尸体所在地点被此类血液污染的土壤中的孢子水平从检测不到到数万不等。通过实验监测了炭疽杆菌在土壤和水中活力的快速丧失，并证明了土壤类型的重要性。杆菌在水中的存活和芽孢形成程度取决于血液被稀释的速度。检查的其他相关参数包括背景菌群、pH值和阳光。
