Equine infectious anemia prevalence in feral donkeys from Northeast Brazil.

This research studies the occurrence of Equine Infectious Anemia Virus (EIAV) in the feral donkey population in Northeast Brazil. The study uncovers EIAV prevalence, potential false positives in testing and hints at the possible existence of new EIAV strains in the tested donkey samples.

Background

• Equine infectious anemia virus (EIAV) infects all members of the Equidae which includes horses, donkeys, and other forms of wild equines. It is a cause of significant concern due to high morbidity and mortality rates.
• Much of the research on EIAV has been conducted on horses with little data available on its effects on other equids such as donkeys.
• With increasing mechanization of transport in Brazil, the economic importance of donkeys is declining. This led to large number of domesticated donkeys being released leading to a significant population of semi-wild donkeys, particularly in Northeastern Brazil.
• This population could potentially harbor and transmit equine diseases like glanders, equine arteritis virus, and EIAV.

Methodology and Results

• The researchers collected serum samples from 367 donkeys in Mossoró city, Northeast Brazil. These tested subjects showed no apparent EIA clinical signs.
• The samples were subjected to several tests including AGID (Agar Gel Immunodiffusion), cELISA (Enzyme-Linked Immunosorbent Assay), and rgp90 ELISA. A further test, immunoblot (IB), was used to verify the results of the rgp90 ELISA
• Results show that 1.6% were seropositive in AGID tests, 3.3% in cELISA, and 14.4% in the rgp90 ELISA.
• However, prominently, 88.7% of those tested positive through rgp90 ELISA were false positives as they could not react with two or more antigens in the immunoblot test. Consequently, the rgp90 ELISA has a similar sensitivity to AGID for donkey serum samples, a finding not previously observed in horse serum samples.
• Another intriguing finding was that 56.9% of the donkey serum samples tested in the immunoblot showed reactivity only to EIAV p26. While this could indictate recent infection with the virus, it is also possible that these results indicate exposure to new strains of EIAV with glycoproteins different from previously characterized strains and hence undetectable by existing techniques.

Implications

• This study portrays a potential risk of EIAV transmission from the semi-wild donkey population in Northeast Brazil.
• The high number of false positives in the rgp90 ELISA test emphasizes the need for validation through confirmatory tests such as immunoblot (IB).
• The significant number of donkey samples reacting only to EIAV p26 sparks the prospect of existence of new EIAV strains with different glycoproteins, underscoring the need for updated detection techniques and further research into EIAV diversity.