West Nile Alert from the Massachusetts Department of Public Health.
There may be good reason to invest in bug spray this year: the Massachusetts Department of Public Health announced just last Friday, Aug. 11, that the West Nile virus has been detected in mosquitoes in Massachusetts for the first time this season.
A sample collected on June 27 in Richmond, a town in Berkshire County, tested positive for the virus. Cases also reported from the Worcester and Boston areas.
Insect and tick bites are relatively common in travelers, they usually only cause minor irritation. However some insect or tick bites can result in skin infections and a number of diseases can be transmitted by these vectors.
Vaccinations or tablets are available to prevent some of these diseases, but for many, bite avoidance is the only way to prevent infection.
Examples of biting insects and the some of the diseases they transmit:
Mosquitoes are attracted by several factors, including the presence of carbon dioxide, heat, odors and movement. The female mosquito requires a blood meal in order to reproduce. There are many mosquito species; some species bite during daylight hours (e.g. Aedes spp.), and some are more active from dusk to dawn (e.g. Anopheles spp.). Diseases mosquitoes transmit include chikungunya, dengue, Japanese encephalitis, malaria, West Nile fever, yellow fever and Zika infection.
Black flies, transmit onchocerciasis (river blindness). They bite during daylight hours and live close to fast-flowing water.
Sand flies, transmit leishmaniasis, are found in many areas of the world and are most active between dusk and dawn; however, they do bite during daylight hours if disturbed. Sandflies usually feed close to the ground.
Tsetse flies transmit African trypanosomiasis (sleeping sickness) and inhabit the dense vegetation and savannah areas in sub-Saharan Africa. They are attracted to dark, contrasting colours, particularly the colour blue, and to moving objects such as cars, canoes, animals and people.
Reduviid bug (Triatome bugs)
Reduviidbugs, transmit American trypanosomiasis (Chagas disease). They inhabit cracks in the walls and roofs or buildings constructed from mud or thatch in Latin America. The infection is transmitted following contact with the faeces of an infected bug.
A number of different species of fleas can feed on humans. Fleas can transmit plague and flea-borne rickettsiosis.
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(note these are not insects but arachnids)
Ticks typically live in long grassy areas. They usually feed on small mammals. On humans, ticks crawl on skin or clothing until they find a suitable place to attach and feed, often at a skin fold in the groin, under the arm, at the scalp line, or at the edge of underclothes. Diseases, such as Crimean Congo haemorrhagic fever, Lyme disease, African tick typhus, and tick-borne encephalitis are transmitted by ticks.
Risk for travelers
According to the World Health Organization (WHO), vector-borne diseases (those transmitted by insects or ticks) account for more than 17 percent of all infectious diseases, causing more than one million deaths annually. The risk of bites and contracting a vector-borne disease for travellers varies with destination and often season and rainfall patterns.
Travelers should research their destination. The CDC is a good resource.) If vaccinations or malaria tablets are needed, a pre-travel appointment should be booked with a health care provider ideally at least four to six weeks before departure. For those with less time, an appointment is still worthwhile.
Travelers should consider if they need to pack protective clothing, insect repellents, insecticide treated bed/cot nets, plug in insecticides and a first aid pack with items to manage insect bites if they are causing irritation (see during travel).
Travelers can use personal protection measures to reduce insect and tick bites. They should be aware of the risk and try to avoid areas known to be heavily infested.
When travelling in areas with malaria it is advisable to wear loose-fitting clothes with long trousers and long sleeves in the evenings. Travelers to areas with a risk of dengue or chikungunya infection (no vaccines available) should cover up during the daytime if possible, as the Aedes spp. mosquitoes that transmit these diseases bite between dawn and dusk.
Clothing can be treated with an insecticide (e.g. permethrin), which kills insects, including ticks, on contact. Permethrin is available in formulations designed to be sprayed on to clothing and this provides protection against mosquitoes, ticks, fleas, lice, sand flies, triatomebugs and tsetse flies. Insect repellents such as DEET can also be applied to natural fibres such as cotton trousers and shirts. However, this repellent can destroy artificial fibres or plastic, the instructions on the pack should be followed.
In tick-infested areas, trousers should be tucked into socks to prevent ticks from crawling up the legs.
Those travelling in Africa in areas where tsetse flies exist should avoid dark blue clothing.
N, N-diethylmetatoluamide (DEET) based repellents are the most effective they have been widely tested under field conditions, and have been used for more than 50 years. DEET is available in several concentrations. Concentrations of 20 percent have been shown to offer protection for 1-3 hours, and higher concentrations provide longer-lasting protection . As the duration of protection plateaus at concentrations higher than 50 percent, there is no need to use repellents with concentrations greater than this.
DEET-containing preparations should not be used in babies younger than two months of age. They can be used in concentrations up to 50 percent in pregnant or breast-feeding women, and in infants and children older than two months. There is no evidence that using DEET on infants and children older than 2 months causes harm. Care should be taken to ensure that repellents are not ingested, and that they do not come into contact with the eyes or mouth.
Repellents should be reapplied at regular intervals, after swimming and in hot, humid conditions when they may be removed by perspiration. When both sunscreens and repellents are used, the repellent should be applied over sunscreen.
Studies show DEET repellents can decrease protection of SPF 15 sunscreen, but there is no evidence that sunscreen reduces efficacy of DEET when used at concentrations above 33%. Repellent activity will reduce more quickly than that of sunscreen if reapplying only sunscreen on top. Therefore repellent will usually need to be reapplied on top of a sunscreen. 30 to 50 SPF sunscreen should be applied to compensate for DEET- induced reduction in SPF. Sunscreen is not required from dusk to dawn.
Research and extensive clinical experience indicate that DEET is very safe when used according to the manufacturer’s instructions.
Insect repellent: advice for travelers
- Use only on exposed areas of skin or natural fibres on clothing.
- Remove with soap and water when the repellent is no longer needed.
- Do not spray directly on the face; apply repellent to hands then to the face to avoid contact with lips and eyes. Wash hands after application.
- Do not apply to cuts, abrasions or irritated skin.
- When both sunscreen and DEET are needed, DEET should be appliedafter
- Sunscreen that is combined with repellent should usually be avoided.
- Picaridin and lemon eucalyptus extract or PMD are available for those who prefer not to use DEET-based products. These repellents have compared favorably with.
- Picaridin should be used in concentrations of approximately 20 percent.
Travelers staying in accommodation without screening should sleep under a net to avoid being bitten at night.
Mesh size in mosquito bed nets should be no larger than 1.5 mm. Nets should be impregnated with permethrin (or other contact insecticides); most nets have been treated prior to purchase. Nets may need to be impregnated with permethrin again after six months of use; long-lasting insecticide nets will generally not need treating frequently .Contact insecticides will kill insects landing on the net and therefore increase the effectiveness.
Travelers can carry a small sewing kit or tape so that repairs can be made if the net develops a hole. Extra equipment for hanging the net can be helpful including extra string or wire hooks.
Measures that cannot be recommended for repelling insects
- Bath oil
- Citronella oil-based repellents (these have very short durations of action)
- Citrosa plant (geranium)
- Garlic: fresh or capsules
- Vitamin B12 complex
- Yeast extract spread
- Electronic (ultrasonic) buzzer devices
- Vitamin B1 tablets
- Tea tree oil
Those with fever (38C or more) or other worrying symptoms after travel should seek prompt medical help. Malaria symptoms can appear up to a year after travel. Travelers should contact their GP if they are concerned about their symptoms being travel-related; antibiotics may be required.
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