Household Bat Guano Farming in Rural Cambodia: Farming Practices, Viruses, Spillover Risks, and Recommended Mitigation Measures in Guano-Producing and Neighbor Households

In Cambodia, farmers construct artificial household bat roosts to collect and sell guano as fertilizer. We investigated farming practices and attendant spillover risks using: 1) surveys on guano production; 2) estimating bat population size and species present using carcasses, visual identification, and audio recordings; 3) surveying guano-producing and neighbor households on water, sanitation, and hygiene practices; and 4) testing guano and household food, water and surfaces for coronaviruses by PCR. Bat roosts are constructed using dried palm leaves with coconut tree and/or steel/concrete supports. Roosting areas ranged from 42-327 m2, bat abundance varied from 0-11,187, guano production was 5-120 kg/week, guano yields were 0.15-0.4 kg/m2/week, and farmers earned ~100-200 USD/household/month. Higher guano production in peak (normally wet) season was associated with greater bat abundance (p=0.016). The lesser Asiatic yellow house bat (Scotophilus kuhlii) was the only bat species identified. Roosts were <20 m from guano-producing households. Neighbors and households’ hygiene risks included not having handwashing stations and not covering food in storage/while drying. Alphacoronaviruses or Infectious Bronchitis Virus were found in 14.6%, 17.3%, 2.9%, 1.4%, and 0.0% of guano, urine, surface, food, and water samples, respectively. While guano farming offers economic benefits, spillover risks exist. Safe guano collection and storage, handwashing, and food covering in guano-producing communities are necessary to mitigate spillover risks.