Even Bacteria Thinks Females are Better
Amanda Fierro (12:00 Micro) is interested in vector-borne diseases, and how microbiotia of insects might modify the behavior of the vector, and their ultimate ability to transmit disease. The relationship between pathogen, host, and vector is complicated, and other players in the web can even further complicate the rate of transmission of various diseases in a population. See this BIO230 summary by a student from last Fall for a counterpoint to Amanda’s summary. In the meantime, here is Amanda’s story:
This topic is from an article on Science Daily based on research performed at Penn State University. The main researcher was Jason Rasgon, PhD. The topic in question for the research was Wolbachia bacteria and its connection to mosquitos and the transmission of West Nile virus. Wolbachia is a genus of bacteria that can be found in arthropods (mosquitos) and nematodes. The bacteria is a parasite that manipulates the reproductive biology of its host to improve and increase its own transmission. It is transmitted from mother to offspring. Males cannot spread Wolbachia to offspring or to any other host. Four mains methods of manipulating its host’s reproductive biology are: “1) feminization of infected males (turning genetic males into females), 2) Induced parthenogenesis (reproduction without males), 3) killing of infected males, and 4) Cytoplasmic Incompatibility (CI), the modification of sperm from infected males resulting embryonic defects and death when sperm fertilize eggs not similarly infected” (University of Rochester, 2011). Past research has suggested Wolbachia bacteria leave mosquitos resistant to pathogens thus inhibiting mosquitos from transmitting those pathogens to humans. An example is the Dengue virus. Because of the research, mosquitos infected with the bacteria are being released into the environment as a strategy to control the Dengue virus. Research also has been done on Wolbachia’s impact on malaria. The studies suggested some malaria-inducing Plasmodium parasites could be enhanced increasing its transmission to rodents and birds.
Rasgon and his team of researchers wanted to discover the bacteria’s effect on West Nile virus. The researchers expected Wolbachia to have the same effects on the mosquito’s West Nile resistance as it did on the Dengue virus. The research team injected adult female mosquitos with the bacteria. After the bacteria was allowed to replicate within the mosquitos, they were fed blood infected with the West Nile virus. Tests showed Wolbachia did not impede the virus. In fact, the mosquitos infected had drastically higher West Nile virus infection rates than the control group after seven days from the date of infection. Rasgon points out a serious complication the results could imply—hosts rendered resistant to one pathogen by Wolbachia could become better pathways for, thus enhancing, other pathogens such as those causing malaria. The researchers also discovered the West Nile virus enhancement due to Wolbachia occurred in combination with the suppression of the genes associated with the mosquitos’ anti-viral immune response. Rasgon and his team plan to do more research to find the mechanism for the West Nile virus enhancement.
The study is important because it is the first study to illustrate, for certain, Wolbachia bacteria enhancing a human pathogen in mosquitos. While West Nile may not be a serious illness for most, it can be deadly to some. According to CDC, about 70-80% of the people infected with the disease do not show symptoms. Those who do, can recover within weeks or months. There also is that 1% of West Nile infected people who develop serious neurologic illnesses. Ten percent of those people will die. Then there is the effect Wolbachia bacteria can have on mosquitos’ malaria resistance. Malaria is much more serious than West Nile. I have always hated insects, especially mosquitos. This gives me more reason to believe bacteria infected insects or any laboratory manipulated organisms should not be released into the environment.