Human WNV Infection Reported Following Equine Necropsy

A veterinary student was diagnosed with West Nile virus (WNV) in May 2009 after performing a necropsy on a 4-month-old Welsh pony from Gauteng, South Africa.

Six days after performing the necropsy, the student developed fever, malaise, myalgia (muscle pain), stiff neck, and a severe headache. A rash appeared two days later and symptoms persisted for approximately 10 days. RNA (genetic material) extracted from the student and the pony identified lineage 2 WNV--a fatal form of the virus previously diagnosed in horses in South Africa in 2008.

WNV is a mosquito-borne flavivirus that circulates primarily in birds and mosquitoes. Humans and horses are considered incidental, dead-end hosts for WNV. An infected horse does not normally pose a risk for infecting humans with WNV since the virus is present at very low levels in the blood, insufficient to infect mosquitoes.

"The student used a bone saw and was the one that removed the brain from the horse and would have had much more exposure to droplets," said Marietjie Venter, PhD, associate professor at the University of Pretoria, South Africa. "At the time, the veterinarians did not take extra precaution besides wearing gloves when doing horse autopsies since they did not see them as being high risk for zoonotic diseases in Africa."

Since no other humans in contact with the pony became ill or developed antibodies against WNV, Venter and colleagues suspect WNV levels could be higher in nerve tissues.

"Veterinarians should therefore be wearing eye protection, gloves, and masks when doing postmortems on animals with fatal encephalitis," advised Venter. The student recovered and is now a practicing veterinarian.

This case report was described in a Letter to the Editor of the journal Emerging Infectious Diseases published in March 2010. More information on WNV in South Africa is available in Venter's article, "Lineage 2 West Nile virus as cause of fatal neurologic disease in horses, South Africa." The article is available online.

About the Author

Stacey Oke, DVM, MSc

Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she's worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

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