Gujarat govt wants pre-monsoon action against sand flies, key carriers of CHPV

With experts expressing concern about the “emerging” Chandipura Acute Viral Encephalitis (CHPV) becoming more widespread in the years to come, the Gujarat government has advised health departments across districts and civic bodies to make preventive action against sand flies — the primary transmitters of the virus — a regular part of pre-monsoon health activities to curb its spread.

Health experts camping in Gujarat to study CHPV, which has so far affected 26 of 33 districts in Gujarat and led to the deaths of 27 children, have maintained that the virus will “continue to exist and spread”, as it is an “emerging virus”.

Experts from a central team that visited Gujarat to study the spread of CHPV, meanwhile, have found anti-CHPV antibodies in several samples of humans, cattles and rodents collected from the affected districts. Health officials told The Indian Express that though the 164 cases of Acute Encephalitis Syndrome (AES) reported so far this year in Gujarat included 61 CHPV cases, the cases have not been reported in a cluster.

Data analysed by the government since 2009 – a presentation on which has been distributed among all district and civic health departments – shows that Gujarat had reported 22 CHPV cases as against 51 AES cases in 2009. It also saw a 100 per cent CHPV mortality rate with all 22 patients dying. Thereafter, a high number of CHPV cases was reported in 2014, at 11, and seven deaths. 2019 saw 10 CHPV cases and five deaths.

In 2024 so far, Gujarat has reported 164 AES cases, of which 61 cases have been confirmed as CHPV. Among the 73 AES deaths so far, 27 patients had CHPV. Until August 12, Panchmahal district had recorded the maximum number of CHPV cases — seven — as well as deaths at four. It was followed by Kutch with three deaths of CHPV patients.

Panchmahal also has the highest number of AES cases at 16, along with Sabarkantha. Of the seven deaths recorded in Panchmahal, three are of AES patients. “In human samples collected from neighbourhoods where cases have been reported, anti-CHPV antibodies have been detected but the exact findings are awaited. Samples of Phlebotomus Papatasi (sand flies) have also been examined and it has been found that male sand flies transmit the virus to the female sand flies, who actually bite,” an expert said.

The expert added, “The study of the samples of cattle and rodents in affected districts, too, has shown clear presence of anti-CHPV antibodies, which indicates that the virus is present in the wider number of hosts and sand flies may only be the primary transmitters…”

CHPV is a viral infection transmitted by sand flies that can cause fever, headache, or encephalitis, leading to convulsions, coma, or death. It causes AES in children and mitigating neurological complications within the first 24 hours is the key to avoid high fatality.

Health officials said that the state has witnessed CHPV outbreaks prior to 2009 as well.

In 2004, Vadodara district had recorded a CHPV outbreak with 70 per cent case fatality rate (CFR) – deaths among total cases – while Gujarat had overall recorded 78.3 per cent CFR but not as a cluster outbreak.

In its August 13 advisory seeking “re-accommodation” of preventive pre-monsoon activities, the state health department said, “CHPV is an emerging pathogen… and the primary vectors are sand flies, particularly of the genus phlebotomus, while potential reservoirs include cattle, although research is ongoing to determine the extend of their role in the life cycle of the virus…”

Maintaining that there is no specific antiviral treatment for CHPV infection, it gives a list of activities to be undertaken for “re-accommodation” – following Union government’s advisory for indoor residual spray (IRS) or insecticide sprayed at homes in villages of affected talukas and actively surveilling affected regions to monitor and identify new cases while also conducting regular field visits. The advisory also suggested repair of broken walls and sealing cracks in houses to reduce vector breeding sites.

Health officials said that in the absence of a direct antiviral treatment for CHPV, prevention is the only way forward. An official from a central Gujarat district that has reported CHPV cases and deaths, said, “The government has been clear that CHPV has to be considered as emerging as a significant disease that gives very little time to react. Since it mostly affects children under 15 years of age, the mortality rate is extremely high. From the recommendations made by expert teams that toured Gujarat, it is clear that the outbreaks could become severe in the years to come…”

“Therefore, spraying malathion in rural homes is to become a regular preventive health activity. The government has also advised that urban

residents should be made aware that structures they occupy should not have any crevices, especially dampness and moisture…”

A civic medical officer said, “As CHPV is spread through sand flies, the only way to prevent the disease is to eliminate sand flies. It can be done by spraying malathion, which has to become a part of the preventive health activities… CHPV will soon spread, just like dengue, malaria or chikungunya, it is not a cluster disease. As post Covid-19 pandemic, infrastructure for diagnostics has been ramped up, higher number of CHPV cases will be reported.”

According to government data, malathion has been sprayed in 16,736 villages comprising 7,45,626 homes as well as 8,317 anganwadis and 30,699 schools.

The IRS has been administered 1,53,959 homes and 8,301 schools till August 12.