Dr. Khamsing Vongphayloth joined Institut Pasteur six years ago.

By Laura Kraft

This post is the third in the “Travel Bug” series by Laura Kraft, a recent graduate from the University of Georgia, who is chronicling her travels in Asia from an entomological perspective. See earlier posts from the series.

While it has only been open about five years, Institut Pasteur du Laos (IPL) already has several different labs up and running, churning out research in the field of medical entomology that is providing data to help Laos in the short term as well as working on toward solutions for the long term.

Laura Kraft

Identifying Insecticide Resistance in Laos

In 2013, Laos saw an epidemic of dengue fever of previously unreported proportions. Dengue cases were found in all provinces of Laos, though the capital of Vientiane in particular was hit hard. In all, 44,171 cases and 95 deaths were reported from around the country. Laos normally receives heavy rainfall from August through October that flushes out breeding sites of local vectors, but irregular rainfall in 2013 may have contributed to the size and scale of the epidemic.

To decrease cases, the Lao government used insecticide for aerial sprays over limited areas the city, but it quickly found that the sprays were not working. Resistance to the insecticide had been found in Thailand, Cambodia, and Vietnam, but none had been reported from within Laos itself. Enter Dr. Sebastien Marcombe.

Fresh from a post-doctoral position at Rutgers looking at insecticide resistance in Aedes albopictus, Dr. Marcombe was hired to find out if the dengue-carrying mosquitoes in Laos also had resistance. Indeed they do. Laos has high levels of resistance in dengue-carrying mosquitoes to all insecticides currently used.

Water-filled cisterns like these in Xaiyamoungkhoun Temple, in Savannakhet, Laos, are a common habitat for mosquito larvae.

When I asked Dr. Marcombe what was different about working in Laos, he chuckled and said, “Everything. Everything is different. The culture is different.” Laos is a country whose people predominantly follow Buddhism. All around Vientiane are beautiful, gold-adorned temples that locals and tourists alike visit frequently to pray, give offerings, or take photos. As Dr. Marcombe explained, some of these temples do not yet have running water. Like many homes in Laos, the monks living at the temples keep a large, open cistern of clean water, typically in the garden or in the kitchen, to use for daily chores such as watering the garden or cooking. This water is often home to mosquito larvae that may become dengue vectors. In the case of the temples, they are hubs where people travel to from around the city, thereby serving as a prime location for mosquitoes to pick up and later transmit dengue to unsuspecting visitors.

The lab run by Dr. Marcombe is now working on a new research project with a new chemistry that may be able to decrease dengue-carrying mosquitoes. The lab will test the juvenile hormone-analogue pyriproxyfen, to be disseminated by wild mosquitoes that pick it up when laying eggs in contaminated water sources. The hope is that the female mosquito can transfer the insecticide to larval breeding sites and reduce numbers of eclosing (maturing) adults. These are techniques that, if successful, could be used to manage future outbreaks of dengue in Laos.

Controlling Mosquito Vectors in Rubber Plantations

Somsanith Chonephetsarath of the Institut Pasteur du Laos draws pictures in her notebook to aid in tracking various clothing combinations being studied to protect workers on rubber plantations from mosquito vectors.

You can’t walk anywhere in Vientiane without hearing the sounds of construction. Local builders are on every block, laying down cement foundations on new high-rises throughout the city. The rapid increase in construction throughout Laos has resulted in a high demand for rubber, causing Laotian farmers to start planting large tracts of rubber plantations in northern Laos. These artificial forests provide the perfect breeding site for mosquito vectors, especially Aedes albopictus, causing concern for the health of the millions of people expected to work on rubber plantations in Southeast Asia over the next decade of projected economic growth in the region.

Rubber plantations work like this: Rubber plants are planted in rows. When mature, workers go out at night to slowly make shallow cuts into the plants. The plants’ milky white latex flows more freely and the plants are less likely to scar and stop flowing when they are cut at night. The latex flows out of the plants into black plastic cups, which are ideal breeding grounds for mosquitoes.

Researchers at IPL are working on identifying which mosquitoes are cause for concern in these immature and mature rubber plantations, as well as which diseases they are carrying. I met with Somsanith Chonephetsarath, a technician helping with some of the new projects being funded by the Michelin Corporate Foundation.

Ms. Chonephetsarath got her bachelor’s degree in environmental science and has been working as a technician at IPL for almost two years. She helped with the preliminary study in the rubber plantations, where she learned to identify mosquitoes that had been collected in the field. Now, she is working on the new study looking at how different clothing options can help to protect the rubber plantation workers.

Fishing through her notebook, Ms. Chonephetsarath pulls out notecards with drawings depicting the different clothing options being used in the study. Options include wearing long sleeves and shorts that have been impregnated with permethrin, wearing treated or nontreated clothing working next to a mosquito coil (a popular mosquito control method in tropical areas of the world that involves burning a spiral-shaped pyrethrum-infused black incense coil), using 20 percent DEET, and wearing long sleeves and long pants. These options are intermixed, creating seven different treatment combinations that the workers use to test attractiveness of mosquitoes. Ms. Chonephetsarath tells me that the workers prefer the mosquito coil and long pants but that the DEET is too smelly and they don’t care for it.

The Michelin Corporate Foundation is also funding a collaboration between IPL and the Institut Pasteur de Cote d’Ivoire in West Africa, a region which also produces large amounts of rubber. Project managers from IPL had the opportunity to travel to Cote d’Ivoire and help their colleagues there choose study sites similar to those used in Laos. With time and a little research, these two developing countries can work together to improve the health and working conditions of rubber plantation workers on two continents.

Doing Taxonomy When There is No Key

Dr. Khamsing Vongphayloth has worked to identify the medically important arthropods of Laos.

Dr. Khamsing Vongphayloth is full of energy when I sit down to talk to him, and you’d have to be to take on the amount of work he is attempting to complete in his career. He first trained as a medical doctor before joining Institut Pasteur six years ago and has since found himself working tirelessly to identify the medically important arthropods of Laos.

He first started identifying mosquitoes of Laos, using classical and molecular techniques to determine the species found in Laos. He then quickly moved on to working on a large project collecting ticks from two large provinces in Laos, in collaboration with the IPL virology team, to determine if any diseases of concern to humans are found in Laotian ticks. The team found Rickettsia sp. in the ticks as well as other bacteria that may be associated with human pathology, which the virology team is investigating further. Richard Robbins, now retired from the Smithsonian Institute, has also helped Dr. Vongphayloth identify the tropical ticks found.

In Laos, people in the villages may encounter ticks in two different ways. First, many villagers keep their livestock under their stilted homes, and this may increase contact with ticks that are found on livestock. They also go into the forest frequently to hunt and gather, and they may pick up ticks there from other wild animals native to Laos. Living in such proximity to different animal species and their associated ectoparasites could cause diseases to jump between these animals and humans, an area that needs further study in Laos.

You can’t flip through a guide book about Laos without seeing suggestions to visit the caves dotting the limestone karst landscape here. These caves also harbor another possible vector of disease: sand flies. While a recent study has made a survey of all pathogens found within the sand flies from caves in two provinces of Laos, Vongphayloth says he is struggling to identify many of the sand flies caught on these trips due to an outdated key that does not include pictures for most taxonomic features, leaving him to piece through spotty descriptions and try to identify tiny, fragile features of these insects.

While he exudes excitement for these projects, Dr. Vongphayloth is most interested to share details about the ongoing work to identify ectoparasites of bats. The project is in collaboration with the National University of Laos, Faculty of Environmental Science. The two institutes come together to catch bats in lightweight nets just outside caves. Dr. Vongphayloth and two student workers from the National University of Laos carefully use forceps to pick off the ectoparasites for identification, while the faculty of the National University of Laos in turn identify the bat species caught. Together, they hope to create a better understanding of the ecology of these animals.

When I finish the interview, I ask Dr. Vongphayloth what his goals are for his career. He would like to put together a checklist for the ticks, sand flies, and bat ectoparasites within the country. “And…” he pauses. Suddenly Dr. Vongphayloth launches into his own pet project—an entomological society of Laos. He explains that most people working in the Department of Entomology at IPL are, like him, from the medical field originally, but it means that they are more interested in the diseases the insects carry than the insects themselves, he complains. He is working on instilling a love of insects in the biology students from the National University of Laos to get more people in Laos interested in entomology (and of course his beloved taxonomy). While all funding for the current research focuses on medically important disease vectors, Dr. Vongphayloth hopes that one day interest in entomological research will allow more funds to be directed at conservation and ecological studies of all insects. And that starts with convincing more students to study entomology, one step at a time.

Laura Kraft is a recent graduate from the University of Georgia who is taking a year off to travel the world before returning home to start a Ph.D. program in the fall of 2017.

(Photos by Laura Kraft)