Sunday, December 27, 2009

Meddling with sex

Your mother may have told you that it's not nice to meddle in the business of others (especially when it's 'nasty business'), but when it comes to mosquitoes, meddling may offer very nice results. Imperial College recently released a report, entitled: "Meddling in mosquitoes' sex lives could stop the spread of malaria", revealing how a particular species of Anopheles gambiae has an easily disrupted sexual process, which when interrupted will prevent that mosquito from breeding.

"The new study focuses on the species of mosquito primarily responsible for the transmission of malaria in Africa, known as Anopheles gambiae. These mosquitoes mate only once in their lifetime, which means that disrupting the reproductive process offers a good way of dramatically reducing populations of them in Africa. When they mate, the male transfers sperm to the female and then afterwards transfers a coagulated mass of proteins and seminal fluids known as a mating plug" (Reeves). Prior to the release of this study, the purpose of this mating plug was misunderstood. Unlike similar substances in other species, the "male mating plug is not a simple barrier to insemination from rival males" (Imperial). Instead it is "essential for ensuring that sperm is correctly retained in the female's sperm storage organ, from where she can fertilise eggs over the course of her lifetime. Without the mating plug, sperm is not stored correctly, and fertilisation cannot occur" (Reeves).

"In Imperial's mosquito labs, the scientists showed it was possible to prevent the formation of the plug in males, and that this stopped them successfully reproducing with females" (Imperial). "In the future", researchers may "develop an inhibitor that prevents the coagulating enzyme doing its job inside male An. gambiae mosquitoes in such a way that can be deployed easily in the field -- for example in the form of a spray as it is done with insecticides". In this way, "we could effectively induce sterility in female mosquitoes in the wild. This could provide a new way of limiting the population of this species of mosquito, and could be one more weapon in the arsenal against malaria" (Reeves).


Imperial College London. "Meddling in Mosquitoes' Sex Lives Could Help Stop the Spread of Malaria." ScienceDaily 22 December 2009. 27 December 2009 .
Reeves, Danielle. "Meddling in Mosquitoes' Sex Lives Could Help Stop the Spread of Malaria." Imperial College London.

Thursday, December 17, 2009

Malaria in Zanzibar

Zanzibar, a" semi-autonomous region composed of two islands off the coast of Tanzania in East Africa," has "drastically reduced malaria" in the past decade. "Zanzibar's aggressive campaign against malaria has reduced infections from as much as 40 percent of its 1.2 million people to less than 1 percent." Recent concerns regarding the reintroduction of malaria to the region sparked a study that tracks the travel patterns of Zanzibar residents by their telephone reception.

"University of Florida researchers at work on a malaria elimination study in Africa have become the first to predict the spread of the disease using cell phone records." Without accessing personal information, "scientists analyzed more than 21 million calls to determine how often residents of Zanzibar travel and where they go." The researchers discovered that "short trips to Dar es Salaam on the Tanzanian mainland nearby, where malaria is relatively uncommon", dominated the travel patterns. "However, they also revealed that a few" Zanzibaris "travel back and forth from more distant areas of Tanzania where the risk of getting the disease is much higher -- posing the greatest threat to elimination."

"Most callers never left Zanzibar, which means they posed no threat of reintroducing the Malaria parasite...About 12 percent did leave the islands, but most of those only visited relatively safe Dar es Salaam, and usually for just one or two days at a time. However, a few hundred residents made trips to regions of western and southern parts of Tanzania, where as many as 40 percent of the residents have the malaria parasite."

Zanzibar has made huge advances against malaria in the past decade; however, those advancements may be reversed by reintroduction. Tanzania, including distant areas that are infected with malaria, must reduce malaria transmission in order to keep infections in Zanzibar low. With concerted effort across Tanzania, the country may eliminate malaria from within its borders.


University of Florida. "Cell Phone Records Used to Predict Spread of Malaria." ScienceDaily 17 December 2009. 17 December 2009 .

Saturday, December 5, 2009


Small bands of males chased game through the savannahs. Females dug along the forest edges for roots, and searched the bushes for edible berries. Humans lived in isolated groups, which constantly moved in search of better subsistence. Then around ten thousand years ago, human settlements sprouted in the plains. Flocks grazed in pastures and humans tended their fields. This social transition "from hunting to agriculture brought permanent settlements, domestication of animals, and changes in diet. It also brought new infectious diseases, in what scientists call an 'epidemiologic transition'" (University).

"Another of these" epidemiologic "transitions came with the Industrial Revolution. Infectious diseases decreased in many places while cancer, allergies and birth defects shot up" (University). Changes to the environment, including shifts in the variety and type of species in a location, cause the emergence of new diseases or the resurgence of old diseases that were once rare.

"Now, it seems, another epidemiologic transition is upon us. A host of new infectious diseases -- like West Nile Virus -- have appeared. And infectious diseases thought to be in decline -- like malaria -- have reasserted themselves and spread" (University). Humans across the globe are falling victim to malaria, an ancient infectious disease, which was once considered to be limited to isolated tropical regions.

According to Pongsiri, a scientist conducting research on the resurgence of infectious disease, the studies "show that emergence or reemergence of many diseases is related to loss of biodiversity." She asserts that this disturbing trend is "not just case-study specific". "Something is happening at a global scale" (University). For example, it is now known that malaria rises and spreads from deforestation. The clearing of forests results in changes to the watershed, including the creation of reservoirs where malaria-carrying mosquitoes can breed. Elevation in regional temperature due to pollution or deforestation can increase the potential habitat of the mosquitoes, causing the disease to spread.

"It is new to think about biodiversity -- and therefore, species and land conservation -- as integral to public health. Until recently, almost no epidemiologists, nor medical schools, were framing questions of human infectious disease prevention in terms of, say, habitat structure, promoting genetic diversity in non-human species, or protecting animal predators as ecosystem regulators. Human diseases, goes the conventional thinking, are best understood and treated by looking at humans."

"Now there is the beginning of a movement to bring epidemiology and ecology together," says Pongsiri.

More info:

University of Vermont. "Biodiversity Loss Can Increase Infectious Diseases in Humans." ScienceDaily 3 December 2009. 5 December 2009 .

Tuesday, December 1, 2009

World AIDS Day

"Malaria and HIV are two of the most devastating global health problems of our time. Together they cause more than 4 million deaths a year" (WHO). On this World AIDS Day, Infectious Bite looks at the relationship between malaria and HIV (the virus that causes AIDS), and discusses new research to treat co-infected (simultaneously infected with both diseases) individuals.

"Our current understanding of the human immune response to malaria and HIV leads us to expect that either infection might influence the clinical course of the other." Ordinarily, "infections are associated with at least a transient increase in HIV viral load" (measure of severity) and it is logical to assume that malaria accelerates "HIV disease progression." On the other side, "immune deficiency caused by HIV infection should, in theory, reduce the immune response to malaria parasitemia and therefore increase the frequency of clinical attacks of malaria" (Whitworth).

According to UNICEF, "HIV infection increases the incidence and severity of clinical malaria. In non-pregnant adults, HIV infection has been found to roughly double the risk of malaria parasitemia and clinical malaria...Although the effect of malaria on HIV has not been so well documented, some recent research is now adding to the growing body of evidence. Acute malaria infection increases viral load, and one study found that this increased viral load was reversed by effective malaria treatment. This malaria-associated increase in viral load could lead to increased transmission of HIV and more rapid disease progression, with substantial public health implications" (UNICEF).

Treatment of malaria is also complicated by HIV. "Artemisinin combination therapy has become the standard of care for uncomplicated malaria in most of Africa. However, there is limited data on the safety and tolerability of these drugs, especially in young children and patients co-infected with HIV" (Shereen). Recently, a "controlled trial was conducted" in Uganda consisting of "HIV-infected and uninfected children aged 4-22)." Participants were randomly designated to receive treatments of artemether-lumefantrine (AL) or dihydroartemisinin-piperaquine (DP). Both therapies were deemed "safe and well tolerated for the treatment of uncomplicated malaria in young HIV-infected and uninfected children" (Shereen).

In conclusion, co-infection of HIV and malaria fuels the spread of both diseases. HIV increases the severity of the episode and the patient susceptibility to malaria infection. Malaria increases the viral load of HIV, thereby elevating the risk of spreading HIV. "Co-infection might...have facilitated the geographic expansion of malaria in areas where HIV prevalence is high. Hence, transient and repeated increases in HIV viral load resulting from recurrent co-infection with malaria may be an important factor in promoting the spread of HIV in sub-Saharan Africa" (Abu). The connection between HIV and malaria also corresponds to the treatment of both diseases. Artemether-lumefantrine and dihydroartemisinin-piperaquine are safe for the treatment of malaria in HIV-infected children. It is also believed that the effective treatment of malaria within HIV-infected individuals may reverse the increased viral load of co-infected individuals.

Abu-Raddad, Laith J. Et. Al. "Dual Infection with HIV and Malaria Fuels the Spread of Both Diseases in Sub-Saharan Africa". Science 8 December 2006.

Shereen, Katrak Anne. Et al. Malaria Journal 2009, 8:272
UNICEF. "Malaria and HIV/AIDS."

Whitworth, James. HIV InSite Knowledge Base Chapter. May 2006.