MOSQUITO, THE SILENT KILLER What could be the most dangerous creature on Earth? Many of us would assume those with razor sharp claws or gnashing teeth. Lions, tigers, jaguars, sharks, and grizzly bears would definitely fit those criteria which instigates plenty of fear in us. However among the deadliest of them all would the small, unassuming MOSQUITO! What makes mosquitoes so dangerous? Despite their innocuous-sounding name – Spanish for “little fly” – they carry devastating diseases. Much more serious than delivering the bites, are the roles of many species of mosquitoes as carriers of diseases. In passing from host to host, some transmit extremely harmful infections such as dengue fever, malaria, Chikungunya and Zika virus.
According to World Health Organization [WHO] estimates, released in December 2015, there were 214 million cases of malaria in 2015 and 438 000 deaths. On the other hand, the year 2015 was characterised by large dengue outbreaks worldwide, with the Philippines reporting more than 169 000 cases and Malaysia exceeding 111 000 suspected cases of dengue fever.
DENGUE FEVER. THE LEADS What is dengue virus? The dengue virus is a mosquito-borne disease, which is usually found within the tropical equatorial belt namely South East Asia, India and some parts of South America since the 1780s. There are over 100 million dengue cases annually affecting as much as 55% of the world’s population. It causes an illness known as the DENGUE FEVER which has been associated with fever, rashes and joint pains. In our country, the Malaysian Ministry of Health reported a record of 336 dengue related deaths in 2015 with an average of 28 in a month. The dengue death toll has risen by 56.3% compared to 215 in 2014. This figure is a major concern among the Malaysian community as the trend of cases and deaths related to dengue has continued to climb since 2011. The death toll this year has reached a total of 109 as of May 2016. How does the virus spread? The virus is mainly spread by the Aedes Aegypti mosquito found in the tropical and subtropical areas of Asia. Capable of also transmitting Yellow Fever, Chikungunya and the recent Zika Fever, these mosquitoes typically feed in the morning or late afternoon and breed primarily in man-made containers such as water tanks, plastic bottles, discarded tires, and flower pots. Once the mosquito is infected with the virus, it is capable of transmitting the virus throughout its lifespan. Who is in danger? Regionally, the west peninsular states of Malaysia were most affected by dengue infections. In year 2014, fifty six percent (56%) of the dengue cases contributed by Klang Valley in which 49% were from Selangor and 7% from Federal Territory of Kuala Lumpur and Putrajaya. The distribution of reported dengue cases were more concentrated in urbanised areas. As shown in a Negeri Sembilan study in 2010, the highest number of dengue cases (81.9%) was reported from Seremban, its largest city. Otherwise, Dengue disease affected all age groups, gender and ethnicity How do you know if you’ve been affected? If you’re at all suspicious that you have been infected with Dengue, a blood sample must be taken within the first week of infection. Symptoms of a typical dengue fever last for about 2 to 7 days which includes high fever, severe headache, pain behind the eyes, unbearable muscle and joint pain, nausea, vomiting, and swollen glands. Some might even have red rashes covering the whole body of theirs. Sometimes a dengue infection would progress into a much fatal disease. Dengue Hemorrhagic Fever also known as Severe Dengue is a deadly complication which has a mortality rate of 50% when left untreated. It is accompanied by abdominal pain, rapid breathing, persistent vomiting, and bleeding gums. Note: Dengue fever can occur more than ONCE which increase in severity with each infection. Prevention is Always Better than Cure. Dengue mosquitoes are urban dwellers like us. Despite living or breeding in natural water reservoirs, like lakes or rivers, they do breed in and out of our houses. Regular checks on flower vases, old automobile tires, buckets, and trash in general, can make all the difference. As there is no vaccines available in our country against dengue, authorities have focused on controlling mosquitoes by issuing a series of recommendations to reduce the risk of being bitten and contracting the dengue virus. Communities have been urged to pull together in an effort to curb infection rates by using insect repellents, light clothing, and cover up as much as possible. Our government has used ample methods to try to control the mosquito population. One in particular, Outdoor Residual Spraying is an efficient technique commonly employed by spraying insecticide outdoors. Another method which made the headlines recently involves the use of Genetically-modified Aedes aegypti mosquitoes to breed with normal Aedes aegypti mosquitoes in the wild. This method was previously used in certain areas of Brazil and managed to kill off 81-95% of the Aedes mosquito population. MALARIA What is Malaria? Malaria is an infection caused by mosquitoes of Anopheline type. Human would get infected when they get bitten by the mosquitoes. The infective agent (Plasmodium parasites) would then transfer from mosquitoes to human. A complicated process would occur in human body (shown in figure below) causing signs and symptoms of the disease. The symptoms are fever, sweating, headache, lethargy, malaise, vomiting, diarrhoea, stomach pain, yellow skin (jaundice), muscle and joint pain. Hence, it is important to seek for immediate medical attention when you encounter these symptoms. Is it common in Malaysia? Malaria is not uncommon in Malaysia, when compared to other mosquito-related diseases like dengue. It is more commonly found in the rural areas (Selangor, Pahang, Kelantan, Perak) and less developed parts of the country. It is important to understand this disease because it contributes to considerable number of cases treated in health clinics, hospitals admission and even death. What should you do to prevent? Malaria can be prevented by taking malaria medications. You can prevent mosquito bites when you stay inside at night (after sunset, before sunrise). Inside the house, it is important to have good screens over the windows and doors to prevent mosquitoes to enter. Or you can sleep under a bed net treated with bug spray. If you are outside, you can wear protective clothing like covered shoes, long-sleeved shirts and long pants. You can also wear special bug spray/cream containing DEET or a chemical called picaridin to prevent mosquito bites. Pregnant women have a higher risk of getting malaria. Infected pregnant women have poorer outcome, such as miscarriage, low weight baby and even death. It is wise for pregnant women to avoid malaria area 2 months after childbirth. Interesting statistical points – Malaria cases are decreasing, from 12,705 cases (in year 2000) to 4,725 cases (in year 2012) o In Peninsular Malaysia, decreasing from 3,918 cases to 1,097 cases (from year 2000 to 2012) o In Sarawak, decreasing as well from 3,011 cases to 1,571 cases (from year 2000 to 2012) o In Sabah, decreasing from 5,776 cases to 2,052 cases (from year 2000 to 2012) – Among human malaria infection, the following Plasmodium parasites are common: o Plasmodium vivax (50.2%) o Plasmodium falciparum (30.7%) o Plasmodium malariae (16.7%) o Mixed infection (2.2%) What is the parasite doing in our body? (Malaria parasites life cycle) CHIKUNGUNYA What is chikungunya and how is it transmitted? Chikungunya is a mosquito-borne viral disease transmitted to humans by infected female mosquitoes. The two species of mosquitoes responsible for chikungunya are Aedes aegypti and Aedes albopictus, which are also the mosquito species that transmit dengue. These mosquitoes are usually found outdoors, and their peaks of activity of are in the early morning and late afternoon. However, the Aedes. aegypti species also readily feed indoors. The onset of illness usually occurs between 4 and 8 days, after the bite of an infected female mosquito. What are the symptoms of Chikungunya? The name “chikungunya” derives from a word in the Kimakonde language, meaning “to become contorted”, which describes the stooped appearance of sufferers with joint pain. Chikungunya has the similar symptoms as dengue fever, and can be misdiagnosed in areas where dengue is common. This disease often manifests as fever, accompanied by joint pain which is very debilitating. The pain usually lasts for a few days or may be prolonged to weeks. Other symptoms include muscle pain, headache, nausea, fatigue and rash. Most patients recover fully, but the joint pain may persist for several months to years in some patients. Serious complications are uncommon, but the disease can cause death in old people. ZIKA, THE NEW ARISING What is Zika? Zika is a disease caused by Zika virus. The primary mode of transmission is through the infected Aedes species mosquito bites. However, Zika virus infection during pregnancy is extremely devastating as it can cause a serious birth defect known as microcephaly. What are the symptoms of Zika? The incubation period between the mosquito bite and the onset of the symptoms is usually 2 to 14 days. The illness is mild with symptoms resolve within 2 to 7 days. Symptoms include fever, rash, joint pain especially in the hands and feet, red eyes, headache. There have also been reported cases of a disease called Guillain-Barré syndrome (GBS), which causes muscle weakness. Can Zika be prevented? Yes. The best way to prevent Zika is to avoid the infected mosquitoes. You can: ● Stay indoors when the mosquitoes are most active. The active periods are during daytime, in the very early morning and in the few hours before sunset. ● Wear closed shoes, long-sleeved shirts and long pants during outdoors. ● Attach a bug repellant that contains a chemical called permethrin on the clothes and gears. ● Drain any stagnant water such as wading pools, buckets and potted plants with saucer. These mosquitoes breed in stagnant water. There is currently no vaccine available to prevent Zika. REFERENCES: Dengue Fever- 1. Mudin RN. Dengue Incidence and the Prevention and Control Program in Malaysia. Int Med J Malaysia [Internet]. 2015 Jun [cited on 2016 Jul 1]; 14(1): 5-9. 2. Bhatia R, Dash AP, Sunyoto T. Changing epidemiology of dengue in South-East Asia. WHO South East Asia J Public Health [Internet]. 2013 [cited on 2016 Jul 1]; 2(1): 23-27. 3. Cheah WK, Ng KS, Marzilawati AR, Lum CS. A Review of Dengue Research in Malaysia. Med J Malaysia [Internet]. 2014 Aug [cited on 2016 Jul 1]; 69(A): 59-67. 4. Dengue Cases Hotspot Area in Malaysia | Komuniti Bebas Denggi [Internet]. Bebasdenggi.my. 2016 [cited 10 June 2016]. 5. Dengue Situation Updates [Internet]. WHO Western Pacific Region. 2016 [cited 10 June 2016]. Chikungunya – 1. World health organisation: Chikungunya [Online] 2016 Apr [cited 2016 May 30] Malaria – 1. Colledge NR, Walker BR, Ralston SH, editors. Davidson’s Principles and Practice of Medicine. 21st Edition ed. Edinburgh: Elsevier Limited; 2010. 2. Malaria. Centers for Disease Control and Prevention; [cited 2016] 3. Management guidelines of Malaria in Malaysia. In: Vector Borne Disease Sector Disease Control Division MoHM, editor. 2014. 1. Zika. Centers for Disease Control and Prevention; [cited 2016]; Available from: http://www.cdc.gov/zika/about/index.html Written by: International Medical University Medical Students: Ang Chun Yiing Chew Ming Wei Lee Hong Wei Lee Jun Long Tiffany Ting Qi Editor : Dr Rajendra Shirahatti