Lusaka – Ebola antibodies found in bats in Zambia seem to show that the species of the disease they have been exposed to match outbreaks as far as 5,000 kilometers away, including the one that’s killed more than 10,000 people in West Africa.
A study, conducted by scientists including Hokkaido University’s Professor Ayato Takada and published in the Journal of Infectious Diseases last week, found the transition of the antibodies for the virus family that includes Ebola coincided with flare-ups in humans from 2005 to 2013. Data for 2014 is still being analyzed.
Scientists are still analyzing samples from last year so they cannot definitively say they coincide with the latest Ebola outbreak, Takada said.
The study explores the theory that straw-colored fruitbats become infected with Ebola from natural reservoirs in central Africa but don’t carry the actual virus to Zambia.
Alternatively, it hypothesizes that the bats themselves act as the reservoirs from which outbreaks into human populations periodically occur. In addition to primates, filoviruses such as Ebola can infect dogs, pigs and duikers, a small species of antelope. Conclusive evidence of either of the hypotheses wasn’t found.
“I do not believe that this bat species serves as a natural reservoir of filoviruses, but our serology data suggest that they can be infected,” Takada said in reply to e-mailed questions on Thursday. “This further suggests that they might have a chance to contact with authentic natural hosts of filoviruses somewhere central Africa.”
The scientists also found evidence of a species of the virus previously only found in Asia. The study was conducted using samples from 748 bats captured in Zambia’s Copperbelt and Central provinces over seven years. The samples were tested for filoviruses, the family of hemorrhagic fever viruses that include Ebola and the closely related Marburg.
“The transition of filovirus species causing outbreaks in Central and West Africa during 2005-2014 seemed to be synchronized with the change of the serologically dominant virus species in these bats,” the scientists said. There is a “need for continued surveillance of filovirus infection of wild animals in sub-Saharan Africa, including hitherto non-endemic countries.”
While no fruit bats have been found to be carrying the actual virus, insect-eating bats are suspected to have sparked the current outbreak in Guinea, Liberia and Sierra Leone.
The fruit bats undertake the world’s second-largest mammal migration between the tropical forests in central and west Africa and northern Zambia in the last three months of the year. About 10 million roost in an area as small as a hectare (2.47 acres) in the country’s Kasanka national park.
“Considering its geographic position, Zambia seems to be a high-risk country that could suffer an incursion of filovirus infection,” the scientists said in the study.
Ebola, which normally kills more than half of those it infects, was first identified in 1976 in the Democratic Republic of Congo and has also been found in countries including Sudan. It is transmitted through bodily fluids.
The prevalence of filoviruses in the bats could be linked to the presence and activity of the species circulating in as –- yet-unknown natural reservoirs, the scientists said in the study, titled “Seroepidemiological Prevalence of Multiple Species of Filoviruses in Fruit Bats (Eidolon helvum) Migrating in Africa.” Almost 10 percent of the samples taken were found to have filovirus-specific antibodies, including Reston ebolavirus, an Asian species that doesn’t infect humans.
The study included scientists from Zambia and found that the species of outbreaks around the continent since 2005 matched the antibodies found in the bats in the same years.
Antibodies are a natural defense the cells of animals and humans produce to combat diseases they come into contact with.
If the bats are the reservoir for the filovirus, the shifting prevalence of each type of the disease in the samples could represent changing proportions in the populations, the scientists said in the study. It could also be that they are only transiently infected in endemic areas in central Africa and don’t carry the virus when they fly to Zambia each year, they said.
The disease that caused the current Ebola epidemic in West Africa may have first been first passed on to a 2-year-old boy from insect-eating bats in a dead tree in a Guinean village in December 2013, scientists said in a study published in the journal EMBO Molecular Medicine at the end of last year.