A 3-year-old Quarter Horse stallion in Polk County, Iowa, recently tested positive for West Nile virus (WNV) on August 22, 2025. This case represents a current outbreak situation, as the horse developed clinical symptoms just six days before testing positive.
The unvaccinated stallion began showing clinical signs on August 16, presenting with several characteristic symptoms of West Nile virus infection:
- Ataxia (loss of coordination and balance)
- Facial nerve paralysis
- Fever
- Lethargy
The horse is currently recovering from the infection.
Significance of West Nile Virus in Horses
West Nile virus is a mosquito-borne disease that can cause serious neurological symptoms in horses. This Iowa case highlights the importance of vaccination, as the affected horse was unvaccinated. The virus typically causes neurological symptoms, and while many horses recover with supportive care, some cases can be severe or even fatal.
The clinical signs observed in this Iowa horse—particularly the neurological symptoms like ataxia and facial nerve paralysis—are consistent with typical WNV presentations in equines. The August timing also aligns with peak mosquito season when transmission risk is highest.
