A study by researchers from the Pune-based Maximum Containment Laboratory (MCL) and Indian Council of Medical Research (ICMR), published in July 2020 in the Indian Journal of Medical Research, found that two human serum samples out of 883, tested for the presence of antibodies, contained antibodies against the Cat Que Virus (CQV). These two samples were from Karnataka. The study was carried out in 2017-18 in order to develop diagnostic tests for CQV as similar species of Culex mosquitoes had spread in India. For this purpose, 1020 human serum samples that showed acute febrile illness during 2014-2017 were collected from Karnataka (806), followed by Maharashtra (116), Kerala (51), Madhya Pradesh (20), and Gujarat (27). However, all these samples were found to be negative for CQV when subjected to the real-time Reverse transcription polymerase chain reaction or RT-PCR test.
Cat Que virus belongs to the genus Orthobunyavirus and is largely found in Culex mosquitoes in China and in pigs, particularly domestic ones, in Vietnam. It was isolated from a jungle myna serum sample in Sagar district of Karanataka in 1961, and was characterised as CQV in 2016 using next-generation sequencing technology. Reports suggest that antibodies against this virus are found in swine, reared locally in China. Thus, it can be said that the virus has formed a ‘natural cycle’ in the local area and is capable of spreading in pigs and other animal populations through mosquitoes.
Another report, published in 2015 in the journal Vector Borne and Zoonotic Diseases states that CQV belongs to the Simbu serogroup and infects both humans and livestock species. The virus was first isolated in 2004 from mosquitoes during the surveillance of arbovirus activity in northern Vietnam. Then, researchers had reported a CQV strain (SC0806), isolated from mosquito samples, collected in China in 2006 and 2008.
Effect on Humans
These mosquitoes can also infect humans. However, there is only a ‘possible disease-causing potential’ of CQV in India because of positivity in human serum samples and the ability of the virus to replicate in mosquitoes. But it could be a potential public health pathogen due to the availability of vector, primarily mammalian host (swine) and confirmation of CQV from jungle myna. It is not yet clear whether the virus is dangerous. However, some other viruses that belong to the same genus as CQV include the Cache valley virus capable of causing meningitis, the La Crosse virus, that can cause paediatric encephalitis, the Jamestown Canyon virus that can cause Jamestown Canyon encephalitis, and the Guaroa virus causing febrile illness.
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Reverse transcription polymerase chain reaction (RT-PCR) is a laboratory technique in which reverse transcription of RNA into DNA and amplification of specific DNA targets using polymerase chain reaction (PCR) are combined mainly to measure the amount of a specific RNA.
Acute Febrile Illness (AFI), also known as Acute Undifferentiated Fever (AUF), Acute Fever (AF) or Short Febrile Illness (SFI), is generally defined as a fever that subsides by itself in three weeks, or lasts for a maximum 15 days. As exact causes of acute febrile illness are yet to be identified a proper definition of the illness sanctioned by medical fraternity worldwide, is not there.
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Courtesy: Indian Express, Wikipedia, netmeds.com