Researchers who looked at the range of viral diseases that affect donkeys and mules have pointed to a worrying lack of studies into the pattern and spread among these animals.
Much of the available knowledge comes from the clinical experience of veterinarians, which is extrapolated from horses to donkeys, they noted.
Rebeca Jéssica Falcão Câmara and her colleagues, writing in the journal Animals, said that most of the viral diseases that affect the Equidae family are required to be reported to the World Organisation for Animal Health (OIE).
Where effective vaccines are absent, control depends on breaking the transmission cycle through testing, segregating infected animals, and reporting the cases to authorities.
Donkeys and mules, they said, are susceptible to infection by equine infectious anemia virus, alphaarterivirus equid (which causes equine viral arteritis), nonprimate hepacivirus (which can cause liver disease), equine herpesviruses, West Nile virus, Saint Louis encephalitis virus, Japanese encephalitis virus, equine influenza virus, rabies virus, Eastern equine encephalitis virus, Western equine encephalitis virus, Venezuelan equine encephalitis virus, and African horse sickness.
“However, in many cases, when infected, they show resistance/low susceptibility to the development of clinical signs,” the review team from Brazil said.
“In this situation, infected animals are hardly identified and remain for long periods as possible sources of infection for horses and other species, including humans.”
They pointed to what they termed the growing devaluation of donkeys and mules, and the shortage of studies related to the epidemiology and progression of viral infectious diseases in these animals.
“As a result, the control of infectious diseases in donkeys and mules is most often compromised.”
They called for robust funding of studies into infectious diseases in donkeys and mules, leading to the development of diagnostic tests specific to them.
The World Organisation for Animal Health and regional agencies in countries where donkeys and mules are abundant should adopt preventive measures against viral spread in these animals, with compulsory disease notification in these populations, they said.
Donkeys, they noted, are often treated as “small horses”. However, donkeys and horses have significant genetic, physiological, and behavioral differences.
“Specific knowledge about viral infectious diseases that affect donkeys and mules is important to mitigate disease outbreaks.”
Currently, the world population of Equidae is estimated at 116.7 million animals, comprising 57.7 million horses, 50.4 million donkeys and 8.5 million mules.
Most donkey and mule populations are concentrated in the Asian continent, as well as in some countries of Central America, South America and Africa. They ensure the livelihood of an estimated 500 million people in poor communities in developing countries around the world.
Donkeys and mules represent about half of the entire domestic equine herd in the world and play an essential role in the lives of thousands of people, primarily in developing countries.
“Despite their importance, donkeys are currently a neglected and threatened species due to abandonment, indiscriminate slaughter, and a lack of proper sanitary management,” they said.
The review team comprised Câmara, Bruna Lopes Bueno, Cláudia Fideles Resende and Jenner Karlisson Pimenta dos Reis, all with the Federal University of Minas Gerais in Brazil; Udeni Balasuriya, with Louisiana State University in the United States; and Sidnei Miyoshi Sakamoto, with the Federal Rural University of the Semi-arid Region in Brazil.
Câmara, R.J.F.; Bueno, B.L.; Resende, C.F.; Balasuriya, U.B.R.; Sakamoto, S.M.; Reis, J.K.P. Viral Diseases that Affect Donkeys and Mules. Animals 2020, 10, 2203.