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).

Sources:
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. http://www.eurekalert.org/pub_releases/2009-12/icl-mim121609.php

Malaria Outbreak in Palm Beach, Florida

Americans living within the borders of the United States feel removed from the problem of malaria. Every so often it's mentioned in passing: Ashton Kutcher buys mosquito nets for children in Africa. The Gates Foundation makes a donation. But, this deadly parasite can infiltrate loosely-screened borders of any country. Malaria only needs to hijack the immune system of a single individual in order to start an epidemic.

In 2003, Palm Beach saw an outbreak of malaria. Victims ranged in wealth and status, profession and hobbies. All but one contracted malaria without having set foot outside the United States. "The hospital staff, inexperienced in working with the disease, failed to correctly identify the infections" (Packard 6). Health-care providers did not "consider malaria as a possible cause of fever among patients who have not traveled," but who experience "alternating fevers, rigors, and sweats with no obvious cause" (CDC). Calling it pneumonia and prescribing antibiotics, the hospitals sent the patients home, where they continued "to infect local mosquitoes" (Packard 6).

Anopheles mosquitoes (the ones that transmit malaria) swarm within the United States. "Palm Beach County was riddled with drainage ditches and canals, which were prime habitats for" mosquitoes (Packard 6). Between 1992 and 2003, "11 outbreaks" including at least twenty cases of "locally acquired mosquito-transmitted malaria" were reported to the CDC (CDC).

It only takes one infected individual to start an outbreak. Patient zero [the first case] may not show outward signs of the disease. This carrier could be on a regiment of symptom-suppressing medications, be recently infected, or even be immune to malaria.

In the particular case of the Palm Beach outbreak, the CDC "concluded that a migrant worker or international traveler might have been involved" (Packard 6). That traveler was not identified. The Palm Beach outbreak "demonstrated the potential for reintroduction of malaria into the United States despite intense surveillance, vector-control activities [vector=agent], and local public efforts to educate clinicians and the community" (Packard 6). It is impossible to prevent malaria from penetrating the US borders when so much of the world suffers heavily from this disease.

Malaria is a global disease. It will only be controlled by a united global assault dedicated to eradication.

Sources:
CDC. "Local transmission...". MMWR Weekly. 26 Sept 2003.

Packard, Randall M. The Making of a Tropical Disease: A short history of malaria. John Hopkins: 2007.

Malaria in Tibet

Rarely a soul considers the risk of malaria while gazing upon the snow-covered Himalayas. Why should one bother? Tibet's high-altitude and cold-weather eliminate malaria-transmitting mosquitoes in most regions. For this reason, many travel books and web sites declare that "there is no risk of malaria in Tibet" (NaTHNaC). Unfortunately, this is absolutely untrue.



"Malaria is endemic in Linzhi Prefecture in the Tibet Autonomous Region (TAR), but the vector [definition: agent] for malaria transmission" was not identified until recently. It is now believed that the mosquito, "Anopheles pseudowillmori[,] is the predominant malaria vector" in the region (Song). Preventative treatment "is recommended...for travel along the valley of the Zangbo river in the extreme southeast" of Tibet (MD). "Anti-malaria medication is recommended for low-lying subtropical areas", particularly "during the rainy season" (Dorje 49).

Tibet is home to the "Falciparum type of malaria," which is considered to be the most dangerous and most deadly strain of malaria. "Various combinations of drugs are being used such as Quinine, Tetracycline or Halofantrine. If falciparum type of malaria is definitely diagnosed, it is wise to get a good hospital as treatment can be complex and the illness very serious" (Dorje 58). Clearly, "protection against mosquitoes and drug prophylaxis against malaria are essential" when traveling to certain areas of Tibet, and all travelers should be aware of the risk of infection (51).

Sources:

Dorje, Gyurme. Tibet handbook: with Bhutan.

Galuzzi, Luca. Photo.

MD Travel Health. "Tibet". 28 August 2009.

NaTHNaC. "China (Tibet)." 28 August 2009.

Song, Wu. Et al. Malaria Journal 2009. "Anopheles pseudowillmori is the predominant malaria vector in Motuo County, Tibet Autonomous Region." 16 March 2009.

World Mosquito Day

The 20th of August is World Mosquito Day. What are you doing to stop malaria?

World Mosquito Day was introduced in "an effort to remind the public about the continuing threat of malaria and other diseases transmitted by mosquitoes" (Mirsky). "Each year, approximately 350 to 500 million people are infected with malaria, killing 1 to 3 million people, mostly young children in Sub-Saharan Africa. Only female Anopheles mosquitoes that had previously bitten a person infected malaria will transmit the disease. Currently there is no vaccine that can provide high level of protection, and malaria parasites have evolved to resist many antimalarial drugs" (NowPublic).

Unfortunately, "it's not a day to celebrate" instead, it's "an awareness day. Ronald Ross of the Liverpool School of Tropical Medicine originated World Mosquito Day in 1897. He's the guy who figured out that mosquitoes carried the malaria parasite. He got one of the first Nobel Prizes for it in 1902" (Mirsky). By the way, he was also knighted in 1911. "Sir Ronald Ross was a British physician born in Almora, India. He had the breakthrough discovery during the dissection of a specific species of mosquito, the Anopheles, previously fed on a malaria patient. Malaria parasite was found on the mosquito and on its salivary glands" (NowPublic).

"112 years later, the fight against malaria is still on" (NowPublic). On this World Mosquito Day, motivate yourself to mention malaria and it's global threat to your peers, acquaintances, or that woman who swats at mosquito while she's waiting for the bus. Together, we can Bite Malaria Back.

Sources:
Mirsky, Steve. "Bite Back on World Mosquito Day." Scientific American. 19 August 2009.
NowPublic. "World Mosquito Day on August 20: Fight against Malaria" 19 August 2009.
Photograph by Hugh Sturrock

Spread of Malaria

Undoubtedly, mosquito bites are the most common way that malaria is spread. Specifically, the female anopheles mosquito is most often the culprit of infection. There are approximately sixty varieties of this mosquito.

How mosquitoes spread malaria:
When an infected individual is bitten by a mosquito, the insect ingests the gametocytes (reproductive forms of the parasite) with the blood. These gametocytes continue in the sexual phase of their cycle. Soon sporozoites (cells that infect new hosts) develop and fill the salivary glands of the mosquito. When the mosquito bites the next person, it injects the sporozoites into the human blood stream along with its saliva.

Most mosquito bites occur between 17:00 (5PM) and 07:00.

Other ways malaria is spread:
Mosquito bites are not the only way that malaria is spread. Other common methods of infection include:

1. Blood transfusions
2. Congenital infection
3. Blood-instrument transmission

Infection through Blood Transfusions:
Infection through blood transfusions is a common problem in areas where malaria is rampant. Even when an individual no longer feels sick from malaria, he/she can still transmit the disease via blood transfusion. Infectious periods differ by malaria strain, but for all strains the malaria may remain in the bloodstream for a number of years.

The duration of time malaria remains infectious by strain:
P. falciparum: 1-3 years
P. vivax: 3-4 years
P. malariae: 15+ years (duration may be for life)

Infections through blood transfusions occur when the blood is not stored properly for a long enough period of time. Most infections occur when blood is stored less than five days. It is rare for blood that has been stored over two weeks to transmit the disease. Frozen plasma is not considered infectious.

Blood can be tested for the infectiousness through the indirect fluorescent antibody test or Enzyme-linked immunosorbent assay (ELISA). Visual examination of the blood manually cannot deliver conclusive results.

Another method to reduce the spread of malaria through blood transfusion is to administer chloroquine to the transfusion recipients. Chloroquine is used to prevent malaria from Plasmodium vivax, ovale and malariae.

Congenital Infection:
"80% of deaths due to malaria in Africa occur in pregnant women and children below 5 years. In Africa, perinatal mortality due to malaria is at about 1500/day" (Malaria Site). Physiological changes within the pregnant woman increases the severity of malaria symptoms. Morbidity may be caused by anemia, high fever, pulmonary edema, puerperal sepsis, and hemorrhage.

The infection may be spread from the mother to the child during pregnancy; however this occurs in less than 5% of malaria cases. Congenital malaria is most common in the first pregnancy. Generally, the placenta protects the child from the infection. However, it is possible for transmission to occur prenatally. Babies who contract the disease congenitally are born with symptoms of malaria. Also, infants born to a mother with malaria may be premature, underweight, or stillborn. Malaria and pregnancy are

Blood-instrument transmission:
Instruments that come in contact with blood (including surgical instruments and needles) may transmit the disease. Much like HIV, malaria can be spread through any contact with the blood of an infected individual. Needles (particularly those used in relation to recreational drugs) may transmit malaria if they are shared. At times, malaria was transmitted unintentionally by medical personnel seeking to inoculate against infectious diseases. Medical personal no longer uses the same needles for multiple individuals, so this risk has decreased dramatically. Intravenous drug users can still transmit the disease if needles are shared between individuals.

Note: People have been intentionally infected with malaria (via needles) as a treatment for syphilis because it produced prolonged high-fevers.

Malaria is a disease that can be treated and in some cases prevented. For information how you can help support malaria research and treatment programs, please visit: The Roll Back Malaria Partnership. Infectious bite is not currently accepting money. All donations should be directed through the individual programs.

Sources:
The Malaria Site. 6 July 2009.
Roll Back Malaria Partnership. 30 June 2009.
World Health Organization: Malaria. 26 June 2009.
Center for Disease Control: Malaria. 26 June 2009.