As a Hubert Fellow, I traveled to Phnom Penh, Cambodia in the summer of 2000 with the mission of establishing a system of surveillance for lyssaviruses and other emerging infectious diseases in bats.

The goal of the project, headed by Dr. Charles Rupprecht from the Centers for Disease Control and Prevention (CDC), is to survey countries in Southeast Asia for the presence of rabies, a lyssavirus. Previously, the CDC had not been able to survey Cambodia due to political turmoil, war, and social unrest.

Our first goal was to determine the location of roosting sites. We made collections in eight different locations around the Phnom Penh region.

The first site we arranged for collection of bats was a restaurant. Bat soup has become a delicacy in Cambodia. You pick out a bat from a cage, much like one might choose a lobster from an aquarium, and it's cooked fresh for your consumption. Some people eat bat as a medicinal remedy for ailments. For example, we were told people drink the blood to help respiratory disorders and eat the eyes to cure eye problems. We primarily collected heads of flying-foxes (Pteropus spp.) from the restaurants.

Another site of collection was the National Museum in Phnom Penh. The museum has exhibits of Khmer artifacts and history, but another main attraction is the hundreds of thousands of bats that live in the ceiling. As soon as you enter the grounds you can hear the calls of the bats- it's quite remarkable. Our entry point to the ceiling was a small 2ft. X 2ft. opening. As one climbs a rickety ladder toward the opening, one can smell the stench of concentrated ammonia from the enclosure. I recall peeping my head into complete darkness and setting my hands on the dust of the guano (bat feces). I had a head-lamp as my only source of light. The ground was covered in guano, plus millions of roaches, fleas, lice, and who knows what else! As horrific as this may sound, it was an awesome experience. The bats lined the ceilings by the hundreds and their bright little eyes reflected back at us from every direction. It was extremely loud due to the high-pitched shriek of the bats, which they use for echolocation.

We were particularly interested in collecting dead or moribund bats, because presumably there would be a higher incidence of disease in these. We collected Tadarida plicata (free-tailed bats) and Taphazous melanopogan (tomb bats) from the museum. After collection, we would take the bats live, each in a small cloth bag, to our lab for processing. There, we would anesthetize them with ketamine and then exsanguinate them intracardially. Serum was separated and stored at -70°C to be shipped to the CDC for antibody testing of lyssaviruses and other viruses such as Nipah, a paramyxovirus that was recently documented as a significant cause of swine morbidity and human mortality in Malaysia. We removed the brains and took tissue impressions from brainstem, cerebellum, hippocampus, and cerebral cortex because these regions consistently have higher loads of virus. We also performed complete necropsies of each bat, taking note of any gross abnormalities. After necropsy we preserved the bats in formalin and stored them in individual containers for future studies. We followed the protocol for RIT (Rapid Immunohistochemical Test) to analyze our impression slides and looked for red intracytoplasmic inclusions (Negri bodies) against the neuronal background.

To date, the CDC has not confirmed a positive case of lyssavirus in the Cambodian samples. However, before we can declare the Cambodian bat population free of rabies we must test hundreds of more bats and sample in other areas. Especially with the growing popularity of bats being used for medicinal purposes and for consumption, the risk of disease transmission to humans is significant.

In addition to rabies and other lyssaviruses, bats have been identified as potential sources for many other diseases, including Nipah virus, equine morbillivirus (or Hendra), Hantavirus, Chagas' disease, and histoplasmosis.

Epidemiological surveillance in bats is vital for the prevention of zoonoses transmissible to humans and domestic animals. To date, there have been two human deaths in Australia to bat lyssavirus, which demonstrates that we cannot forgo surveillance even where there has been no previous evidence of the disease. Although most human cases of rabies around the world are due to exposure to domestic animals, wildlife reservoirs, such as bats, present a source for emerging strains.

I would like to extend a warm thank you to Dr. Corrie Brown, of Pathology at the University of Georgia College of Veterinary Medicine, for her encouragement and support in my qualifying for this project. My deepest gratitude also, to the O.C. Hubert Charitable Trust, the CDC Foundation and Dr. Charles Rupprecht for making this incredible opportunity possible. Thank you also to Dr. James Olson for his hospitality and assistance with the project, Joe Walston, and Emily Meseck.

Note: The O. C. Hubert Endowed Fellowships in International Health offers an opportunity for medical and veterinary students in the U.S. to spend several weeks working on priority health problems in countries around the world and to see public health issues first-hand. Students thus far have traveled to Brazil, Malawi, China, Romania, Cambodia, Vietnam and the Philippines. Applications and opportunities for calendar year 2001 will be available after January 15. To receive these documents by e-mail, please send your request to Patsy Bellamy: prb1@cdc.gov or call (404) 639-4774.

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