Malaria enters the US

"Nearly a dozen cases of Malaria has been confirmed here in the United States. All of the cases were acquired in Haiti after the January 12th, 2010 earthquake" (Gibbons). "Seven emergency responders, three Haitian residents now in the United States and one American traveler are known to have caught malaria in Haiti after the Jan. 12 earthquake, United States health officials said Thursday. Malaria is endemic throughout Haiti, so Haitians now living outdoors and relief workers are 'at substantial risk for the disease,' the Centers for Disease Control and Prevention said" (McNeil).

"Haiti already had a problem with malaria, which is spread by mosquitoes that will have more places to breed in the cities and towns wrecked by the giant quake" (Reuters). Displaced people living in temporary shelters our outdoors are at substantial risk of contracting malaria. Health workers who flooded to Haiti after the earthquake to offer aid are also at risk. "U.S. health officials advise people travelling to Haiti should take medications to prevent malaria" (UPI).

"Six out of eight patients, including seven emergency responders, had been advised to take drugs to prevent malaria but had not done so, the PAHO experts said." Three of the cases that the CDC cited "occurred among Haitian residents traveling to the United States and one case involved a U.S. resident who was visiting Haiti. All are expected to recover fully" (Reuters).

Individuals in Haiti are still at risk. "Each year, Haiti reports about 30,000 confirmed cases of malaria to the Pan American Health Organization, but the CDC estimates as many as 200,000 may occur each year. According to the CDC, malaria transmission peaks after the two rainy seasons -- November to January and again during May to June" (Reuters). The peak season is still months away, but anti-malarial medications are already needed to treat those who are infected and reduce the number of possible cases.

"There is no vaccine against the parasite that causes the illness[,] and it quickly evolves resistance against drugs"; however some drugs are known to treat and reduce malaria illness (Reuters).

The CDC indicates that "anyone traveling to Haiti should take drugs to help prevent infection" (Reuters).


Sources:
Gibbons, Sabrina. WSB News. "Malaria from Haiti Now in US." 4 March 2010.

McNeil, Donald G Jr. The New York Times. "U.S. Warns of Malaria Risk in Haiti". 4 March 2010.

Reuters. "Travelers from Haiti bringing Malaria to the US." 4 March 2010.

UPI. "Malaria Drugs for those going to Haiti." 4 March 2010.

Pirate parasites

Parasitic Plasmodium invaders swarm the bloodstream, set up a base camp in the liver, and commandeer healthy red blood cells. These parasites "enter the body from the saliva of a mosquito" and send plague upon their victim (American). Malaria, the deadly and devastating disease that kills nearly a million people every year, is caused by the Plasmodium parasites as they pillage the human body for their own reproduction and survival.

"Inside the blood cells" of the malaria patient, "the parasites replicate and also begin to expose adhesive proteins on the cell surface that change the physical nature of the cells in the bloodstream" (American). Medical experiments "show that infected red blood cells are stiffer and stickier than normal ones." In "later stages of the disease" the cells can be "up to 10 times stiffer" than healthy red blood cells. These infected cells may also anchor onto "endothelial cells lining the vasculature, affecting the normal blood flow. This explains some of the common symptoms of malaria, such as anemia and joint pain" (American).

The parasites avoid a whirlpool of blood cell death in the spleen by anchoring in the safe harbors of the blood vessels. "Sticking to the walls of blood vessels is a survival mechanism for the parasite. In order to develop completely, it needs several days inside a red blood cell. Even though parasitized cells are nearly invisible for the immune system, they may be destroyed in the spleen while circulating freely in the bloodstream" (American).

Brown University professor George Karniadakis and student Dmitry Fedosov study "how malaria infections affect the physical properties of red blood cells, and alter normal blood flow circulation. In particular, they examine an increase in blood flow resistance, and dynamics of infected cells in the bloodstream." The properties that they measure are "used in modeling the flow of red blood cells in people infected with malaria" (American).

Fedosov says, "Our model predicts the dynamics of malaria-infected RBCs in the bloodstream, which anticipates the possible course of the disease." Each infected human contains a slightly different map and provides a unique environment that the parasites must navigate. The researchers recently discovered "that temperature fluctuations of infected red blood cell membranes measured in experiments are not directly correlated with the reported cell properties, hence, suggesting significant influence of metabolic processes" (American).

Hypothesizing on the metabolic processes that affect the patients' body temperatures, the researchers "measured an increase in resistance to blood flow in the capillaries and small arterioles during the course of malaria and found that parasitized red blood cells have a "flipping" motion at the vessel wall that appears to be due to stiffness of the infected cells. The developed models will aid to make realistic predictions of the possible course of the disease, and enhance current malaria treatments" (American).

Play the parasite game (NobelPrize.org site), and see if you can navigate your way to the liver.

Sources:
American Institute of Physics. "Measuring and Modeling Blood Flow in Malaria." ScienceDaily 22 November 2009. 27 November 2009 .

Malaria in Vanuatu

"Vanuatu, an archipelago of over 80 islands in the South Pacific, ranks behind only the Solomon Islands for having the highest rate of malaria infections. Malaria in Vanuatu has been getting steadily worse since the 1980s, which is why UCSF scientists are among the medical professionals working hard to control malaria in this region" (UCSF).

Malaria parasites are found in all regions of Vanuatu, and "[t]ransmission occurs from December to May. Either mefloquine (Lariam), atovaquone/proquanil (Malarone), or doxycycline may be given. Mefloquine is taken once weekly in a dosage of 250 mg, starting one-to-two weeks before arrival and continuing through the trip and for four weeks after departure." Malarone is a "combination pill taken once daily with food," the side-effects of which are "typically mild". Doxycycline "is effective," against malaria in Vanuatu "but may cause an exaggerated sunburn reaction, which limits its usefulness in the tropics" (MD Health). It is important to know that "Chloroquine is NOT an effective antimalarial drug in Vanuatu and should not be taken to prevent malaria in this region" (CDC). Malaria resistance to Chloroquine is becoming increasingly throughout the world as the parasite adapts.

"UCSF researchers, with funding from the Bill and Melinda Gates Foundation", "are conducting a large-scale household-level survey of malaria treatment and prevention practices in Vanuatu. Over 900 households on four islands (out of a total of more than 80, although only a few are populated) have participated in the study. Researchers also collected blood samples from all members of the households selected for the survey, which will permit them to link survey responses on prevention and treatment practices to biological markers" (UCSF).

For more information on the study, please visit UCSF web page.

Sources:
CDC. Malaria in Vanuatu. http://wwwnc.cdc.gov/travel/destinations/Vanuatu.aspx

MD Travel Health. 'Vanautu'. http://www.mdtravelhealth.com/destinations/oceania/vanuatu.php

UCSF. Malaria Prevention. http://medschool.ucsf.edu/news/features/public_service/20060619_Malaria.aspx

Popcorn parasite

Who would have thought that infecting "mosquitoes with a bacterial parasite could help prevent the spread" of blood parasites like malaria and lymphatic filariasis? If you guessed that it might, then you are either clever or very well-informed. For the rest of us, it is an exciting idea that may aid in "the control of...mosquito-borne parasites" (Wellcome).

Researchers have infected mosquitoes with a strain of Wolbachia, which is a bacterial parasite that infects insects and other arthropod species (Werren). The strain known as wMelPop, and nicknamed 'popcorn', can halve the lifespan of infected mosquitoes. "Mosquito-borne parasites such as the filarial nematode or the malaria parasite require an incubation period between ingestion and transmission, so only older mosquitoes" are "infective. Skewing the mosquito population towards younger individuals reduces the number of infectious insects." In the case of lymphatic filariasis, a parasitic worm that is transmitted by mosquitoes, wMelPop has also been shown to encourage "the mosquito's immune system to attack" the parasite that it hosts (Wellcome).

The 'Popcorn' strain may reduce the number of mosquitoes and the likelihood that they will transmit a parasite that is deadly to humans. Researchers are "currently looking at whether infecting other species of mosquito, such as Anopheles gambiae - the mosquito responsible for the majority of malaria infections - with wMelPop will have a similar effect and help inhibit malaria transmission as well as filariasis transmission."


Sources:

Kambris Z et al. Immune activation by life-shortening Wolbachia and reduced filarial competence in mosquitoes. Science 2009.

Wellcome Trust (2009, October 2). Parasite Bacteria May Help Fight Spread Of Mosquito-borne Diseases. ScienceDaily. Retrieved October 4, 2009, from http://www.sciencedaily.com­ /releases/2009/10/091001163601.htm

Werren, J.H.; Guo, L; Windsor, D. W. (1995). "Distribution of Wolbachia in neotropical arthropods". Proc. R. Soc. London Ser. B 262: 147–204.

Monkey malaria

"Researchers in Malaysia have identified...an emerging new form of malaria infection" that is a "potentially deadly" strain of the disease (ScienceDaily). "Malaria kills more than a million people each year. It is caused by malaria parasites, which are injected into the bloodstream by infected mosquitoes" (Daneshvar).

"Recently, researchers at the University Malaysia Sarawak...showed that P. knowlesi, a malaria parasite previously thought to mainly infect only monkeys - in particular long-tailed and pig-tailed macaques found in the rainforests of Southeast Asia - was widespread amongst humans in Malaysia." After several similar reports, P. knowlesi has been deemed "the fifth cause of malaria in humans" (ScienceDaily).

P. knowlesi malaria is particularly dangerous because it "can easily be confused with P. malariae", a more benign form of malaria (ScienceDaily). Under the microscope, the two strains appear nearly identical, but the strains are very different in severity and deadliness. "One of the most significant findings of the study is that Plasmodium knowlesi was found to have the ability to reproduce every 24 hours in the blood -- meaning infection was potentially deadly. This, according to the researchers, meant early diagnosis and treatment were crucial" (Kounteya).

A universally low platelet count is another curious characteristic of this strain of parasite. "In other human forms of malaria, this would only be expected in less than eight out of ten cases." But, "all of the P. knowlesi patients - including those with uncomplicated malaria - had a low blood platelet count...The researchers believe the low blood platelet count could be used as a potential feature for diagnosis of P. knowlesi infections." (ScienceDaily).

"Recently, there have been cases of European travellers to Malaysia and an American traveller to the Philippines being admitted into hospital with knowlesi malaria following their return home" (ScienceDaily). This deadly strain of malaria may potentially spread across the globe and infect millions if it is not adequately treated and controlled.

Sources:
Daneshvar C, et al. Clinical and laboratory features of human Plasmodium knowlesi infections. Clin Infect Dis. 2009;49(6):852-60.

Kounteya Sinha. The Times of India. "Monkey malaria spreads to humans in South-east Asia". 11 September 2009.

ScienceDaily. In Humans. Retrieved September 13, 2009, from http://www.sciencedaily.com­ /releases/2009/09/090909103004.htm

Schweinsaffe im Tierpark Berlin (photo)

Genetically-engineered malaria vaccine

Scientists have created a "weakened strain of the malaria parasite" that "will be used as a live vaccine against the disease." This type of vaccine "has proven successful in eradicating smallpox and controlling diseases such as flu and polio" (Walter). It has already been advantageous in animal studies, and it is hoped that it will prove successful when it enters human trials (slated for early next year).

Professor Alan Cowman, head of the Walter and Eliza Hall Institute's Infection and Immunity division, said that "in developing the vaccine the research team...deleted two key genes in the Plasmodium falciparum parasite - which causes the form of malaria most deadly to humans" (Walter). "The deletions did not affect the parasites throughout most of the life cycle," but "by removing the genes the malaria parasite is halted during its liver infection phase, preventing it from spreading to the blood stream where it can cause severe disease and death" (Cowman; Walter). The photo to the left shows the parasitic cells during the liver stage (WT is normal).

The fact that the deletion of the genes "did not result in any observable defect during blood-stage replication...indicated that gene deletions did not affect the sexual stages of the parasite" (Cowman). "Although two genes have been deleted the parasite is still alive and able to stimulate the body's protective immune system to recognize and destroy incoming mosquito-transmitted deadly parasites" (Walter).

"Similar vaccines" have "been tested in mice and offered 100 per cent protection against malaria infection." Cowman "said it was hoped the vaccine would produce similar results in humans" (Walter). Whenever working with an attenuated [definition: weakened] strain of a disease, mutation is always a concern. Some people fear that the parasite will mutate to a viable form, thereby infecting individuals through the vaccine. "Professor Cowman said it was unlikely the weakened parasites used in the vaccine would regain their potency as the genes had been deleted from the genome and could not be recreated by the parasite" (Walter).

The fact that two essential genes have been deleted "make it extremely unlikely that the attenuated parasite vaccine could restore its capacity to multiply and lead to disease." The scientists believe that their "genetically attenuated parasite approach provides a safe and reproducible way of developing a whole organism malaria vaccine," which has the unique ability of being nearly 100% effective (Walter).


Sources:
Cowman, Alan F. et al. "Preerythrocytic, live-attenuated Plasmodium falciparum vaccine candidates by design." 10 June 2009.

Walter and Eliza Hall Institute (2009, August 24). First Genetically-engineered Malaria Vaccine To Enter Human Trials. ScienceDaily.

Malaria in Cambodia

Researchers recently announced that a strain of malaria parasite in Cambodia has become resistant to "arteminisnin-based drugs". This development "could put millions of lives at risk" (Resistance). "Artemisinin-based combination therapies are the recommended first-line treatments of falciparum malaria in all countries with endemic disease. There are recent concerns that the efficacy of such therapies has declined on the Thai-Cambodian border, historically a site of emerging antimalarial-drug resistance" (Dondorp).

"Choloroquine and sulfadoxine-pyrimethamine resistance in P.falciparum emerged in the late 1950s and 1960s on the Thai-Cambodian border and spread across Asia and then Africa, contributing to millions of deaths from malaria. "Since the first reports of chloroquine-resistant falciparum malaria in southeast Asia and South America...drug-resistant malaria has posed a major problem in malaria control. By the late 1980s, resistance to sulfadoxine-pyrimethamine and to mefloquine was also prevalent on the Thai-Cambodian and Thai-Myanmar (Thai-Burmese) borders, rendering them established multidrug-resistant (MDR) areas" (Wongsrichanalai).

"Artemisinins have been available as monotherapies in western Cambodia for more than 30 years, in a variety of forms and doses, whereas in most countries...they have been a relatively recent introduction." An "extended period of often-suboptimal use, and the genetic background of parasites from this region, might have contributed to the emergence and subsequent spread of these new artemisinin-resistant parasites in western Cambodia." "In contrast, artemisinin derivatives have been used almost exclusively in combination with mefloquine on the Thai-Burmese border, where parasitologic responses to artemisinins remain good, even after 15 years of intensive use" (Dondorp).

The recent study compared patients from Cambodia with those from Thailand. "Researchers (Wellcome Trust-Mahidol University Oxford Tropical Medicine Research Program) discovered that on average "patients in Thailand were clear of malaria parasites within 48 hours" but Cambodian patients averaged 84 hours" (Resistance). "These markedly different parasitologic responses were not explained by differences in age" and "adverse events were mild and did not differ significantly between the two treatment groups" (Dondorp). Dr Arjen Dondorp declared, "Our study suggests that malaria parasites in Cambodia are less susceptible to artemisinin than those in Thailand". Currently, artemisinin is used to "clear the parasites at an early stage, preventing them further maturing and reproducing" (Resistance). Since its introduction, "artemisinin-based combination therapies has reduced the morbidity and mortality associated with malaria" (Dondorp).

However, with the new emergence of resistant malaria parasites, the number of malaria related deaths is expected to rise. "Measures for containment are now urgently needed to limit the spread of these parasites from western Cambodia and to prevent a major threat to current plans for eliminating malaria"(Dondorp). "Sixty percent of Cambodia's landscape poses a malarial risk. One million Cambodians are infected with malaria each year" (Wongsrichanalai). "Malaria remains one of the primary causes of mortality in Cambodia... Sustained efforts through local and national malaria control will be necessary to contain Cambodia's malaria epidemic" (Wongsrichanalai).

Image from Donorp. Graph from comparative study between Cambodia and Thailand, and how well the drugs treat malaria.


Sources:
Dondorp AM, Nosten F, Yi P, et al. Artemisinin resistance in Plasmodium falciparum malaria. N Engl J Med 2009;361:455-467.
Population Reference Bureau. "Fewer Malaria Cases in Cambodia."
"Resistance to Malaria Drug Reported in Cambodia." US World News. 29 July 2009.
Wongsrichanalai C, Pickard AL, et al. Epidemiology of drug-resistant malaria. 2002 Apr.

Halting Malaria Transmission

Brought to my attention by @sarahsearle

"Researchers at the Johns Hopkins Malaria Research Institute have for the first time produced a malarial protein" that can "generate a significant immune response" and be used to create "a potential transmission-blocking vaccine" (Parsons). Antibodies produced in response to the protein, inhibit the "sexual development of the malaria-causing parasite, Plasmodium, as it grows within the mosquito".

"According to the study, a single-dose vaccine provided a 93 percent transmission-blocking immune response, reaching greater than 98 percent after a booster was given several months later" (Parsons).

Humans are on the verge of successfully creating a vaccine that may inhibit the spread of malaria. In the late 1980s, scientists understood the possibility of transmission-blocking immunity. They discovered that individuals can "develop immunity that suppresses the infectivity of the sexual stages of the parasite." This "immunity is antibody mediated and is directed against the parasites in the mosquito midgut shortly after ingestion of blood by a mosquito." In 1987, scientists declared that "This immunity could be expected to have significant effects on the natural transmission of P. vivax malaria" (Mendis).

"Development of a successful transmission-blocking vaccine is an essential step in efforts to control the global spread of malaria" (Kumar). This study indicates that "it is possible to gradually reduce malaria transmission to a point of almost eradication" (Parsons).

Sources:
Kumar, Nirbhay.

Mendis, K N. Y D Munesinghe, Y N de Silva, I Keragalla, and R Carter. Malaria transmission-blocking immunity induced by natural infections of Plasmodium vivax in humans. 1987 February.

Parsons, Tim. Vaccine Blocks Malaria Transmission in Lab Experiments. 22 July 2009.

Malaria in China

China has seen a resurgence of Malaria in recent years. "China reported about 24 million malaria cases in the 1970s, the number of cases declined to several hundred thousand by the late 1990s. However, the disease recently has "re-emerged" in China's central and southern provinces, possibly as a result of insufficient prevention work" (Global).

China suffers from Falciparum malaria which "is the most deadly among the four main types of human malaria. Although great success has been achieved since the launch of the National Malaria Control Programme in 1955, malaria remains a serious public health problem in China" (Lin). "Falciparum malaria was endemic in two provinces of China during 2004–05" (Lin). "The 'level one' areas have an annual malaria incidence of more than one case per 10,000 people, while the 'level two' regions have an annual incidence of less than one per 10,000 people" (Global).


Map provided by Travax

"Imported malaria was reported in 26 non-endemic provinces. Annual incidence of falciparum malaria was mapped at county level in the two endemic provinces of China: Yunnan and Hainan. The sex ratio (male vs. female) for the number of cases in Yunnan was 1.6 in the children of 0–15 years and it reached 5.7 in the adults over 15 years of age" (Lin).

The recent resurgence of malaria in China has prompted "China's Ministry of Health" to draft a "plan to eliminate malaria from the country by 2015" (Xinhuanet). "Central and local governments will provide funding for the malaria control programs, an unnamed official from the health ministry's disease control department said." "The plan aims to reduce malaria incidence to less than one case per 10,000 people in high-burden regions and to no cases in low-burden regions between 2010 and 2015" (Global).

Sources:
Global Health Reporting. "Malaria | China Develops Nationwide Malaria Eradication Plan". 10 April 2009.

Lin, Hualiang. Liang Lu, Linwei Tian, Shuisen Zhou, Haixia Wu, Yan Bi, Suzanne C Ho, Qiyong Liu. Spatial and temporal distribution of falciparum malaria in China.

Xinhuanet. "China lays out plans to quell malaria" http://news.xinhuanet.com/english/2009-04/10/content_11163891.htm 10 April 2009.