Experimental transmission of a granulocytic form of the tribe Ehrlichieae by Dermacentor variabilis and Amblyomma americanum to dogs

Oscar S. Anziani From the Department of Entomology, College of Agriculture (Anziani, Barker) and the Department of Veterinary Parasitology, Microbiology, and Public Health, College of Veterinary Medicine (Ewing), Oklahoma State University, Stillwater, OK 74078.

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 DVM, MS
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S. A. Ewing From the Department of Entomology, College of Agriculture (Anziani, Barker) and the Department of Veterinary Parasitology, Microbiology, and Public Health, College of Veterinary Medicine (Ewing), Oklahoma State University, Stillwater, OK 74078.

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 DVM, PhD
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R. W. Barker From the Department of Entomology, College of Agriculture (Anziani, Barker) and the Department of Veterinary Parasitology, Microbiology, and Public Health, College of Veterinary Medicine (Ewing), Oklahoma State University, Stillwater, OK 74078.

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 PhD

Summary

Transstadial transmission of granulocytic Ehrlichieae in dogs was attempted using ticks, Amblyomma americanum and Dermacentor variabilis. Ticks were exposed by feeding as nymphs on acutely infected pups; adult ticks then fed to repletion on susceptible adult dogs that were monitored daily for signs of infection. Evidence of transmission was not observed in control dogs or in those exposed to D variabilis. In contrast, dogs exposed to A americanum developed serologic or clinical evidence of infection, but organisms were not seen in blood smears until corticosteroids were administered, causing recrudescence and accompanying parasitemia. At 12 days after subinoculation of blood obtained from donor adult dogs, before corticosteroids were administered, a febrile response, thrombocytopenia, and appearance of morulae in neutrophilic granulocytes were observed in 2 susceptible recipient dogs.

Summary

Transstadial transmission of granulocytic Ehrlichieae in dogs was attempted using ticks, Amblyomma americanum and Dermacentor variabilis. Ticks were exposed by feeding as nymphs on acutely infected pups; adult ticks then fed to repletion on susceptible adult dogs that were monitored daily for signs of infection. Evidence of transmission was not observed in control dogs or in those exposed to D variabilis. In contrast, dogs exposed to A americanum developed serologic or clinical evidence of infection, but organisms were not seen in blood smears until corticosteroids were administered, causing recrudescence and accompanying parasitemia. At 12 days after subinoculation of blood obtained from donor adult dogs, before corticosteroids were administered, a febrile response, thrombocytopenia, and appearance of morulae in neutrophilic granulocytes were observed in 2 susceptible recipient dogs.

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