Tackling Fatal Tick Fever, Researchers Break Ground With Macaques

BETHESDA, Md. (CN) – Researchers reported Monday that they have found a suitable animal model to study a viral disease that is fatal in nearly one of every three cases.

The yellow dots in this scanning electron micrograph represent viral particles of the Crimean-Congo hemorrhagic fever budding from the surface of cultured epithelial cells. (Image via NIAID)

Crimean-Congo hemorrhagic fever, according to the letter published this morning in the journal Nature Microbiology, is spread by ticks in the Middle East, Asia, Africa and parts of Europe.

Experts at the National Institute of Allergy and Infectious Diseases, part of the National Institutes of Health, note in the letter that treating the virus has been complicated by the difficulty finding a suitable animal model for research.

Using a viral strain isolated from a tick found in Nigeria, previous studies have involved mice with weakened immune systems to cause infection.

Though researchers have been unable to consistently replicate human disease in studies of larger animals, Monday’s letter announces a successful pilot study where a strain of the virus known as Kosovo Hoti was isolated from the blood of someone the fever killed.

The strain was introduced to African green monkeys, rhesus macaques and cynomolgus macaques, and two of three cynomolgus macaques developed disease. Also known as long-tailed or crab-eating macaques, the cynomolgus monkey is native to Southeast Asia where it is seen as an invasive species in some places, including Hong Kong and New Guinea.

A crab-eating macaque and her juvenile at Djuanda Forest Park, West Java, Indonesia. (Image via Wikipedia)

In a subsequent larger study, severe infection occurred in eight cynomolgus macaques, half of which were inoculated intravenously. The other infected four were given a combination of intravenous and under-the-skin inoculation.

By contrast, four cynomolgus macaques that were inoculated under the skin did not suffer severe infection: two developed mild signs of infection and the other two remained symptom-free.

Monday’s letter notes that the disease progressed in the cynomolgus macaques in the same manner as it does for most infected people.

After a three- to four-day incubation period, the prehemorrhagic period lasts three to five days. The hemorrhagic period then lasts two to three days, followed by either recovery or death.

The NIAID notes that the range of conditions its study found in the study of cynomolgus macaques, from no fever symptoms to severe disease, could mean that this animal model will help researchers examine how the infection progresses and interacts with the immune system — with developing treatments and vaccines being the ultimate goal.

In the first segment of the study, none of the African green monkeys or rhesus macaques showed signs of disease after various inoculation methods.

Elaine Haddock is the lead author of the study.

%d bloggers like this: