Insecticide Susceptibility Status of Phlebotomus (Paraphlebotomus) Sergenti and Phlebotomus (Phlebotomus) Papatasi in Endemic Foci of Cutaneous Leishmaniasis in Morocco

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In Morocco, cutaneous leishmaniasis is transmitted by Phlebotomus sergenti and Ph. papatasi. Vector control is mainly based on environmental management but indoor residual spraying with synthetic pyrethroids is applied in many foci of Leishmania tropica. However, the levels and distribution of sandfly susceptibility to insecticides currently used has not been studied yet. Hence, this study was undertaken to establish the susceptibility status of Ph. sergenti and Ph. papatasi to lambdacyhalothrin, DDT and malathion.

Methods

The insecticide susceptibility status of Ph. sergenti and Ph. papatasi was assessed during 2011, following the standard WHO technique based on discriminating dosage. A series of twenty-five susceptibility tests were carried out on wild populations of Ph. sergenti and Ph. papatasi collected by CDC light traps from seven villages in six different provinces. Knockdown rates (KDT) were noted at 5 min intervals during the exposure to DDT and to lambdacyhalothrin. After one hour of exposure, sandflies were transferred to the observation tubes for 24 hours. After this period, mortality rate was calculated. Data were analyzed by Probit analysis program to determine the knockdown time 50% and 90% (KDT50 and KDT90) values.

Results

Study results showed that Ph.sergenti and Ph. papatasi were susceptible to all insecticides tested. Comparison of KDT values showed a clear difference between the insecticide knock-down effect in studied villages. This effect was lower in areas subject to high selective public health insecticide pressure in the framework of malaria or leishmaniasis control.

Conclusion

Phlebotomus sergenti and Ph. papatasi are susceptible to the insecticides tested in the seven studied villages but they showed a low knockdown effect in Azilal, Chichaoua and Settat. Therefore, a study of insecticide susceptibility of these vectors in other foci of leishmaniasis is recommended and the level of their susceptibility should be regularly monitored.

Authors: Chafika Faraj, Souad Ouahabi, El Bachir Adlaoui, Mohamed Elkohli, Lhoussine Lakraa, Mohammed ElRhazi and Btissam Ameur

Full Article: Insecticide susceptibility status of Phlebotomus (Paraphlebotomus) sergenti and Phlebotomus (Phlebotomus) papatasi in endemic foci of cutaneous leishmaniasis in Morocco (PDF)

Source: Parasites & Vectors 2012, 5:51 doi:10.1186/1756-3305-5-51

Published: 19 March 2012

Copyright: © 2012 Chafika Faraj et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Malaria in KwaZulu Natal

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QUESTION

How many people are infected by malaria in KZN?

ANSWER

By “KNZ” I assume you mean KwaZulu Natal (for the benefit of other readers, this is a region of South Africa, in the north-eastern portion of the country). KZN is one of the few parts of South Africa that experiences malaria transmission, though effective control measures have reduced its impact as a public health threat.

Up until 1996, South African policy had been to use DDT (even though it was a banned substance) to control mosquito populations, and malaria levels had correspondingly been low. However, after cessation of spraying with DDT, the number of malaria cases increased, to a high of over 40,000 cases in the 1999/2000 malaria season (in KZN, malaria is most commonly transmitted during the wet summer months, from November to May). Since then, the use of DDT as an insecticide has been reintroduced (along with other public health measures, such as switching to artemisinin-based combination therapies for first-line malaria treatment), and the burden of malaria has plummeted.

The most recent data I could find reported less than 3500 cases for the 2001/2002 malaria season, and zero cases in 2002/2003 (though the data I found were only up to February 2003). Efforts to coordinate malaria control between South Africa, Mozambique and Swaziland have also contributed to the success of reducing malaria transmission in the region.

Does Malaria Still Exist?

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QUESTION

does malaria still exist?

ANSWER

Yes, malaria still exists, and is responsible for 250 million cases of illness every year, of which about 700,000 result in death. So it is a very serious global health problem!

Some countries, such as the United States, have managed to successfully eliminate malaria through a combination of vector control strategies (i.e. spraying for mosquitoes, reducing the presence of water bodies where mosquitoes breed, etc) and better health infrastructure for diagnosis and treatment. This strategy has also been successful in other settings, such as the Mediterranean and much of the Middle East, as well as even in some high transmission tropical settings such as Malaysia (particularly in urban areas).

The widespread distribution of long-lasting insecticide treated bednets has further assisted in malaria prevention in high transmission areas. However, much of the rest of the world is still struggling to control malaria, though the number of deaths is dropping every year, and some organisations hope to reduce malaria mortality to zero by the year 2015.

If you have taken medications for malaria, please help Malaria.com by taking our Malaria Survey. Thank you!

Malaria Prevention

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QUESTION

what is the prevention of malaria?

ANSWER

There are many ways in which to prevent malaria. I’ll break them down into three categories: 1) medical prevention, 2) protection from getting mosquito bites and 3) vector control.

1) Medical prevention

Malaria can be prevented using certain medications. Taking drugs to prevent a disease is known as “chemoprophylaxis”, and so these drugs are often referred to as “malaria prophylactics”. There are several different types of malaria prophylactic: the most common ones are chloroquine, a mix of atovaquone and proguanil (marketed as Malarone), mefloquine (marketed as Lariam) and doxycycline. The mode of taking these medications vary (Lariam is taken once a week, for example, whereas the others are usually taken once every day), and they also have different restrictions and side effects. Chloroquine is not effective in areas where local forms of malaria have become resistant, for example, and Lariam is not recommended for people with a history of mental instability, as it is known to cause hallucinations and otherwise impair consciousness. Here on Malaria.com, we are actually currently running a survey on side effects of malaria prophylactic drugs, so if you have ever taken medication to prevent malaria, please take the survey: Malaria Medication Side-effects Survey: Treatment and Prophylaxis

It is worth noting that these drugs have not been tested for long term use, plus they can be expensive if taken for an extended period of time. As such, they may not be appropriate for people living in endemic areas for malaria. However, medication can be useful for preventing malaria in high risk groups, even when they are living in a malaria endemic area. One example is the use of intermittent preventive treatment (IPT) for preventing malaria infection in pregnant women, infants and young children. For more information on this, please see the review article written by Dr Felicia Lester for this website: http://www.malaria.com/research/malaria-pregnancy-preventive-treatment

2) Protection from getting mosquito bites

This section links in with the more general vector control strategies, which will be discussed below. Since malaria is transmitted through the bite of infected mosquitoes, preventing mosquito bites is a very effective way of reducing malaria incidence. One of the most popular methods for personal protection, especially in areas where malaria is endemic, is through sleeping under a mosquito bednet. The mesh prevents mosquitoes from being able to fly close to the person sleeping; however, if there are holes in the net, or the person skin is pressed directly against the mesh, the mosquito may still be able to bite them. This is where insecticide-treated bednets come in – they are impregnated with mosquito repellents to stop mosquitoes from biting through the mesh or passing through holes. Newly developed long-lasting insecticide treated bednets (LLINs) are even more effective, in that they don’t require “re-dipping” to maintain the level of repellent in the fibres, and so can protect a person for several years without losing efficacy. These LLINs have been instrumental in reducing cases of severe and fatal malaria, especially among pregnant women and young children, who are often targeted by bednet distributors.

Other methods for preventing mosquito bites include wearing long-sleeved clothing and personal application of mosquito repellent, particular those containing a percentage of DEET, which is a very effective insecticide. These measures should be especially taken in the evening, early morning and at night, which is when the Anopheles mosquitoes that carry malaria are most active.

3) Vector control

Finally, malaria can be prevented from reducing numbers of mosquitoes directly. Some methods target the adult mosquitoes; one such initiative is indoor residual spraying (IRS), whereby the inside of a house is sprayed with an insecticide to kill mosquitoes. Twelve different insecticides are approved by the World Health Organisation for this purpose, though pyrethroids are among the most popular, as they can be used on a variety of surfaces, do not leave a visible stain and can also protect against other insect pests, such as bedbugs.

Other methods for vector control focus on other parts of the mosquito lifecycle. Mosquito larvae require stagnant freshwater for their development, so some projects have worked to eliminate standing water sources, such as unnecessary ditches and puddles, which reduces the amount of habitat available for mosquitoes to lay their eggs and sustain larvae. Other programmes have spread insecticides directly in stagnant water to kill the larvae, or sought to introduce fish or other aquatic organisms, such as copepods, which consume mosquito eggs and larvae. This latter biological control approach is popular because it can also supply an area with fish for local consumption, and doesn’t contaminate water sources with chemicals.

Malaria Eradication and Water Quality

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QUESTION:

How will the eradication process of the mosquito larva influence the quality of the water?

ANSWER:

That’s a very interesting question. The answer is that it depends a lot on the way in which the mosquito larva are controlled. The usual, traditional method is through the application of insecticides. Many of these are known to have severe negative effects on water quality, particularly through being non-selectively toxic and therefore killing lots of other aquatic life as well as the mosquitoes. Moreover, some are known for their effects on animals further up the foodchain; the most famous example of this being DDT, which was used to kill adult mosquitoes. It was discovered that this pesticide resulted in birds laying eggs that had very thin shells, preventing the chicks from hatching successfully. As such, it was banned in most developed countries. Modern insecticides used for mosquito larva reduction have been developed to target mosquitoes specifically; a popular one in the USA is methoprene, which interferes with the mosquitoes’ growth hormones, preventing development into adults. Microbial compounds, which are not dangerous to other organisms, are also sometimes used.

Another approach is through the use of natural enemies of the mosquito larvae, notably certain species of fish and dragonflies. These will eat mosquito larvae and pupae, thus naturally reducing numbers, and with little undue effect on water quality (although in some contexts, such as reservoir water, there may be concerns with stocking the water source with large numbers of fish).

Malaria in Southern United States

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QUESTION:

Why is there not a prevalence of malaria in the southern United States when we are bitten almost daily by the “little beasts?”

ANSWER:

Malaria once was relatively common in the southern United States. Transmission used to be possible due to the favorable climatic conditions for the development both of the mosquito as well as the malaria parasite. Huge advances in the control and treatment of malaria were made directly as a result of increased interest in the disease after the US occupation of Cuba and the building of the Panama Canal in the early years of the 20th century. This vastly reduced the number of cases of the disease, but the final, concerted effort to eradicate malaria came in the 1940s.

This was due to a federal public health program called the National Malaria Eradication Program (NMEP), and as a result of its actions, malaria transmission was halted throughout the United States by 1951. The program was launched in 1947, coordinated by the newly formed Communicable Disease Center (now the Center for Disease Control and Prevention, or CDC) and mostly involved reducing the number of mosquitoes in and around people’s homes. This was done through the wide-spread spraying of DDT—during the years of NMEP, it has been estimated that more than 6.5 million homes were sprayed with the insecticide. Alongside spraying, mosquito breeding habitats were also removed, through wetland drainage, and human monitoring and treatment efforts were stepped up. By 1949, malaria was no longer considered a disease of public health importance, and it was declared eradicated from the United States in 1951.

Having said that, the species of mosquito that transmit malaria still exist in the USA, and particularly in the southern states, which means that there is always a risk of small, localized outbreaks of the disease, particularly during hot and wet seasons.

Climate change may also increase the zones where malaria is at risk of being able to develop within the United States. For this reason, the CDC continually monitors the small number of cases reported each year in the USA (there were about 1500 cases in 2007—all but four of these cases, however, were the result of travelers to malarial areas outside of the USA bringing the disease back with them) to ensure that they are prepared and well-informed should an outbreak arise.