Yellow Fever Vaccine Reactions in Peru: Follow-up

CDC released a statement discussing the deaths associated with Yellow Fever Vaccinization, in Peru. See original post on subject here. A total of four deaths have been associated with the YF vaccine, given in Peru, as a governmental response to potential outbreaks.

The vaccines implicated are all from the same lot numbers and manufacturer: Bio-Manguinos in Brazil. The investigators are still attempting to determine if there is a problem with the vaccine itself or a unique reaction to the vaccine, only in those who died.

Adventure Doc Yellow Fever Page

Yellow Fever Vaccine Recalls in South America

I received an e-mail today from one of the many, many travel and tropical medicine listserves I am following. There has been recall of the YF vaccine manufactured by BioMaguinos, headquartered in Brazil. The recall is in response to the 4 Peruvian deaths associated with recent vaccinization, all from the same lot, of this implicated vaccine. Of note, there are 9 lots in total that are being recalled, at present. This larger recall, involving other lots, makes you wonder how widespread the problem vaccines are? This vaccine is widely used in South America.

According to the WHO/PAHO statement, 3 of the 4 deaths have been classified as “acute viscerotropic disease following yellow fever vaccination” after autopsy, with the 4th case pending. There have only been 37 cased of confirmed or suspected acute viscerotropic disease following yellow fever vaccination, since the disease was first recognized in 2001.

From that same WHO/PAHO statement: “The estimated risk for viscerotropic disease following YF vaccination ranges from 0.1 to 0.3 per 100,000 vaccinated persons overall; a higher risk has been documented in persons older than 60 years.”

The vaccine used in the USA is from a different company: Sanofi Pasteur.

The Yellow Fever vaccine is a live virus vaccine. This means you are actually getting a bit of the virus, that is alive, injected into you. There are other vaccines that make use of killed bacteria or viruses and inject them, letting your body develop immunity without risk of infection. The ubiquitus MMR (measles, mumps, rubella) vaccine is a live virus vaccine. Commonly given to children in developed nations, it is never to be given to people with weakened immune systems or pregnant women.

The Yellow Fever vaccine is given as a one shot dose and offers protection from YF for 10 years, according to WHO re-imminuzation requirements. I have commonly heard that the YF vaccine is believed to provide immunity for up to 30 years, although there is limited formal data to this.

Contraindications to receiving the YF vaccine include an altered or weak immune system (because you cannot fight off the live virus used to immunize you), pregnancy (the live virus can harm the fetus), allergy to eggs (the vaccine is produced by injecting the virus into eggs, allowing it to multiply) and age less than 9 months old (immune system might not be able to fight off the live virus).

Check out more about Yellow Fever over at AdventureDoc.org and my original post about this, a few days ago.

Mosquito Bite Prevention

Mosquito Bite Prevention

700,000,000 people get a disease from a mosquito, each year. Of those diseases, 1 out of 17 people currently alive will die from the disease.

The species to know about are Aedes, Culex and Anopheles. These are the bad girls that carry diseases such as malaria, yellow fever, dengue fever and filariasis. I say “bad girls” because on the female mosquito bites mammals. The growth on new mosquitoes requires a blood meal. The males are content to only feed from flowers. Certain types of mosquitoes prefer animals, some prefer humans and some feed from both.

Attraction:

What attracts mosquitoes is not fully clear, yet. Mosquitoes do have developed senses of vision, thermal/heat sense and smell. They use all of their senses to find food. It is believed that the olfactory (smell) sense is the most important in finding victims.

During the daytime, dark colored clothing and movement help a female mosquito “lock on” to its target, at long range. As the mosquito nears her prey, the senses of smell and thermal sense take over. Carbon Dioxide and Lactic Acid are two of the most studied mosquito attractants. CO2 is mainly found in exhaled breaths and lactic acid can be found on the skin when muscles are being used, as in exercise. Lastly, skin temperature and skin moisture guide the mosquito to where they want to bite, on the body. It is widely assumed that certain species of mosquito prefer different body parts; hands, face, feet, etc. This could be due to the differences in local skin temperatures. Scented soaps, cologne, lotions and hair products can also attract mosquitoes.

As for personal preference, adults are preferred over children. Men are more commonly bitten than women and larger people get bit more than smaller people, possible due to their increased CO2 output. It also appears my wife is preferred over to me.

Chemical Repellents:

DEET (N,N Diethyl 3 Methylbenzamide) is the gold standard of insect repellent. It has been well studied for over 50 years and provides protection not only against mosquitoes but also flies, chiggers, ticks and fleas. The concentrations of DEET available range from 5% to 100% and the higher the concentration of DEET, the longer the time of protection. Concerns over long term exposure to high doses of DEET have led to the US Military to adopt a 35% slow release formula. The medical literature disagrees over a formula that accurately predicts number of hours of protection and DEET percentage. One study indicates a 4 hour protection with 50% DEET while another indicates 12.5% DEET protected for 6 hours. Products with 20-35% DEET generally provide adequate coverage for most instances. There are reports of skin irritation occurring more frequently with percentages greater than 35%. The Pediatricians advise nothing more than 10% DEET for children less than 12 years old. Use of DEET with sun-block lowers the efficacy of the sun-block. So, more frequent applications of sunscreen will be needed for adequate solar protection. The DEET spray is applied to the skin, first. Sunscreen is applied over the top of the DEET spray. I remember this because the DEET protects your blood and stays the closest. Sunscreen protects against the sun, which is further away. DEET is a well studied and commonly used chemical. High dose DEET has been shown to not be a neuro-toxin. There have been several cases of encephalopathy (brain swelling), mostly in children, with prolonged exposure and inappropriate use of DEET. DEET works by inhibiting signals from the mosquitoes’ antennae and making it hard for them to find you.

Avon Skin-So-Soft is known to be a mosquito repellent. Lab studies showed a 30-minute protection time against Aedes mosquitoes. Ideas as to why it is a repellent center around either fragrance of the cream or the chemicals it contains, benzophenone and diisopropyl adipate.

Permethrin is an insecticide that kills or stuns bugs. Permethrin is effective against mosquitoes, ticks, flies, chiggers and fleas. The chemical does not easily absorb into the skin. This is applied to clothing, bed nets or screens, as a spray.

Citronella is known as the “natural” mosquito repellent. Derived from a plant, Cymbopogon Nardus, the oil has a lemon-like scent. Studies have shown that burning citronella candles and/or incense decrease the number of insect bites, for those near to the candles or incense.

Timing is Everything

Most species of mosquitoes bite at dawn and dusk. Avoiding being outside will lessen your chances of bites. When you are sleeping at night, in open air environments, a bed net is definitely shown to decrease bites. Often, those staying in nicer hotel rooms, with climate control, do not need netting. Open windows mean a need for netting.

Learn more about mosquito carried diseases such as Malaria, Dengue Fever and Yellow Fever over at www.AdventureDoc.org

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