West Nile study sparks call for virus surveillance in Saudi Arabia

More than 70% of horses and nearly 10 percent of humans in the study had been exposed to the virus.
Photo by Vivian Arcidiacono

More than 70 percent of horses enrolled in a study in the eastern part of Saudi Arabia were found to carry antibodies against West Nile Virus, prompting scientists to propose vaccination.

Researchers Khaled Alkharsah and Adel I Al-Afaleq, writing in the journal Infection and Drug Resistance, said vaccinating horses in Saudi Arabia against the mosquito-borne virus would massively reduce the prevalence of disease from the virus.

West Nile was first isolated in 1937 from the blood of a local woman in the West Nile district of Uganda. Since then, it has become endemic in countries across Africa, the Americas, the Middle East, West Asia and in Australia.

Many species can be infected, in particular birds, humans, and horses. Infections in humans can cause fever and, although neurological problems are less common, they have the potential to cause serious illness and even death.

About 20% of West Nile infections in horses result in disease development, of which 90% involve neurological symptoms. The disease has fatality rates of 30 to 40%.

Alkharsah and Al-Afaleq, with Imam Abdulrahman Bin Faisal University, set out to investigate the seroprevalence of West Nile antibodies in humans, horses, and pigeons in the Eastern Province of Saudi Arabia.

Blood samples were collected for testing from 323 humans, 147 horses, and 282 pigeons from two regions, Al-Ahsa and Al-Qatif, in the east.

The percentage of antibodies against West Nile in the human population was found to be 9.6%, with males more than twice as likely to have been exposed.

In horses, the prevalence was much higher. The pair found that 105 of the horses – that’s 71.4% – had antibodies against the virus.

No significant differences were found in the frequency of West Nile antibodies among different age groups in either humans or horses. Notably, 72.7% of the horses had detectable antibodies against the virus by the age of 1.

In total, 150 of the 282 pigeons – 53.19% – had West Nile antibodies.

The authors said their study provides the first evidence of West Nile antibody detection in humans and pigeons in the region.

The seroprevalence in horses was high, they said. Two previously published studies on seroprevalence in horses in Saudi Arabia had also found high levels of exposure, they noted.

“Overall data indicate that West Nile Virus is endemic in Saudi Arabia,” they said. “These findings suggest that more attention should be given to the diagnosis and reporting of West Nile Virus infections in humans and animals.”

More effort was also warranted to measure the clinical burden of the virus. “Additionally, implementation of West Nile Virus vaccine in horses would massively decrease the morbidity.”

The authors said a surveillance program is required, as has already been established in several countries.

Alkharsah KR, Al-Afaleq AI. Serological Evidence of West Nile Virus Infection Among Humans, Horses, and Pigeons in Saudi Arabia. Infect Drug Resist. 2021;14:5595-5601

The study, published under a Creative Commons License, can be read here


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