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First Record of Coccidiosis in Wolves, Canis lupus

Coccidiosis infects a variety of species including such canids as Coyotes (Canis latrans) and domestic dogs (Canis lupus familiaris) (Pence and Custer 1981). However, to our knowledge the disease has not been reported for Wolves (Canis lupus) (Brand et al. 1995), despite the radio-monitoring of many hundreds of Wolves for survival and mortality, including over 600 in the Superior National Forest, Lake County, Minnesota, alone (Mech and Frenzel 1971; Mech 1986, and unpublished; Van Ballenberghe et al. 1975). The present report documents the occurrence of coccidiosis in three Wolf pups from two litters in the Superior National Forest, and the death of at least two of them from this disease.

We live-trapped, weighed, and obtained blood samples (Mech 1974) from four Wolf pups (671, 673, 675, and 699) from one litter in July 1997, and a pup (723) from the litter of an adjacent pack in November 1997 (Table 1). Three of the pups were 31-36% lighter than the expected weight for well-fed wolves of their age and sex (Van Ballenberghe and Mech 1975), and two to four of their six hematological values were aberrant (Table 1). Veterinarians implanted 24.6-gm, mortality-sensing radio-transmitters intra-abdominally in the four littermates, and we released the pups back in their rendezvous sites where caught within 24 hours and monitored their signals at least twice daily. Based on radio-tracking, all these animals moved around similarly, but after 13 and 53 days, two of them died (Table 1). The other two survived at least through 19 November 1998 and 21 October 1999. We live-trapped, weighed, blood-sampled, and radio-collared the fifth pup of our sample (Wolf 723) 14 km east of the other two pups on 4 November 1997, but he never recovered from his capture and handling.

Table 1. Clinical information about Wolf pups that died from coccidiosis and their littermates that survived, Lake County, Minnesota, 1997.
Wolf Number Sex Date Caught Weight Kg % Under-
Date Died Hematology2
671 M 6 August 8.3 41 - 42 13.4 4.4 32 962 22.52
673 M 6 August 8.1 42 - 482 15.72 5.0 33 972 15.0
675 F 7 August 8.3 32 29 September 502 15.52 5.1 31 982 27.92
699 M 6 August 8.9 36 19 August 342 10.82 3.72 32 91 30.42
7233 M 4 November 15.5 31 5 November 37 10.02 4.8 272 78 13.7
1Compared with data from Van Ballenberghe and Mech (1975).
2Outside of standard error of mean values of large sample of Wolf pups from same area, 1969-1972 (Seal et al. 1975).
3From pack adjacent to the other Wolves.

We retrieved Wolf 675 within 24 hours of her death and froze the carcass. Within 8 hours of Wolf 699's death, we found only his transmitter, a length of small intestine, and a fecal bolus. The rest of his remains apparently had been eaten by his pack mates. We froze both specimens. We also froze the carcass of Wolf 723.

On 6 January 1998, the junior author examined all the specimens. Toxicological testing for antimony, bismuth, mercury, and inorganic arsenic (Reisch test) and strychnine and brucine (thin layer chromatogtraphy) were all negative. Electron microscopy of feces (Muneer et al. 1988) from all three Wolves and the fecal sample revealed no virus. Histopathological examination of the intestines showed no evidence of parvoviral enteritis. However, both carcasses had hemorrhagic feces in the large intestines, and the severely autolyzed intestine of the third Wolf (Wolf 699) also had hemorrhage. The intestinal mucosa of both Wolves had many various developmental stages of Isospora oocysts in both enterocytes and in the lamina propria.

We concluded that Wolves 675 and 699 died of severe coccidiosis, and that is also the most probable cause of death for Wolf 699. This is the first record that we could find of coccidiosis in Wolves.

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