Nelson Thomas A, Gregory David G, Laursen Jeffrey R
Department of Biological Sciences, Eastern Illinois University, Charleston, Illinois 61920, USA.
J Wildl Dis. 2003 Jul;39(3):593-9. doi: 10.7589/0090-3558-39.3.593.
Canine heartworm (Dirofilaria immitis) disease affects wild canids and may be a factor impacting the health and population dynamics of coyotes (Canis latrans). Coyotes may serve also as a potential reservoir for transmission of these parasites to domestic dogs. We investigated 920 coyotes harvested by hunters and trappers throughout Illinois (USA) from 1995-1997. The objectives of the study were to: 1) survey the regional prevalence and intensity of heartworms in coyotes in Illinois, 2) determine whether heartworm intensity correlates with physical condition, particularly body weight and winter fat levels, and 3) evaluate the relationship between heartworm infections and the reproductive success of females. Prevalence of heartworms statewide was 16.0%. Prevalence was significantly higher in males (17.7%) than in females (14.1%; P = 0.04) and was higher in the older age-classes (P < 0.0001). The regional prevalence of heartworms increased from northern to southern Illinois. Intensity ranged from 1 to 111 with a mean of 8.7 (SD = 13.2) worms. Intensities did not differ significantly between sexes (P = 0.53) or among age-classes (P = 0.84). Most infected coyotes had low intensity infections, 78.2% carried < 12 heartworms, 11.6% had 12-24 worms, and 10.2% were infected with > 24 worms. Body weights were not correlated with the presence of heartworms, nor were levels of kidney fat and marrow fat. However, reproductive success was lower in infected females. The percent of yearling females that bred was lower among infected females, as was the number of offspring produced by adults > or = 3.5 yr old. Our study demonstrates that heavy infections adversely affect fur quality and reduce fecundity of some females, but these effects are small and few coyotes (4.1%) had enough worms to trigger them. Coyote populations have increased in Illinois during the past 20 yr, but prevalence and intensity of heartworm disease appears to have changed little in that period. We conclude that heartworm disease is only a minor factor influencing coyote population dynamics in Illinois.
犬心丝虫（恶丝虫）病会影响野生犬科动物，可能是影响郊狼（犬属）健康和种群动态的一个因素。郊狼也可能是这些寄生虫传播给家犬的潜在宿主。我们调查了1995年至1997年期间美国伊利诺伊州各地猎人及捕兽者捕获的920只郊狼。该研究的目的是：1）调查伊利诺伊州郊狼中心丝虫的区域流行率和感染强度；2）确定心丝虫感染强度是否与身体状况相关，特别是体重和冬季脂肪水平；3）评估心丝虫感染与雌性繁殖成功率之间的关系。全州心丝虫的流行率为16.0%。雄性（17.7%）的心丝虫流行率显著高于雌性（14.1%；P = 0.04），且在老龄组中更高（P < 0.0001）。伊利诺伊州心丝虫的区域流行率从北部到南部呈上升趋势。感染强度范围为1至111条，平均为8.7条（标准差 = 13.2）。不同性别（P = 0.53）和不同年龄组（P = 0.84）之间的感染强度没有显著差异。大多数感染心丝虫的郊狼感染强度较低，78.2%的携带少于12条心丝虫，11.6%的有12至24条，10.2%的感染超过24条。体重与心丝虫的存在无关，肾脂肪和骨髓脂肪水平也无关。然而，感染雌性的繁殖成功率较低。感染雌性中一岁龄雌性的繁殖比例较低，3.5岁及以上成年雌性的后代数量也较少。我们的研究表明，重度感染会对皮毛质量产生不利影响，并降低一些雌性的繁殖力，但这些影响较小，只有少数郊狼（4.1%）的心丝虫数量足以引发这些影响。在过去20年中，伊利诺伊州的郊狼数量有所增加，但在此期间心丝虫病的流行率和感染强度似乎变化不大。我们得出结论，心丝虫病只是影响伊利诺伊州郊狼种群动态的一个次要因素。
