Animal-Associated Hazards

Animals in general tend to avoid human beings, but they can attack if they perceive threat, are protecting their young or territory, or are injured or ill. Although attacks by wild animals are more dramatic, attacks by domestic animals are by far more common. Animals cause injury through bites, kicks, blunt trauma, or the use of horns or claws. Further damage can occur if injuries become secondarily infected, and may result in serious systemic disease. As a general rule, travellers should never try to pet, handle, or feed unfamiliar animals, domestic or wild, particularly in areas of endemic rabies. Young children should be closely supervised while around wild or domestic animals not known to have been properly vaccinated against rabies. All bite wounds should receive prompt attention and cleansing to reduce the risk of infection. (See Rabies section for more information.) CDC also recommends that travellers receive a tetanus booster before departure, if they have not had one within the last 5 to 10 years, in the event of a puncture wound or bite.

Macaques, a type of monkey, pose an additional threat as potential sources of herpes B virus. Herpes B virus is related to the herpes simplex viruses, which cause oral and genital ulcers. Herpes B infection is rare in humans, and all documented cases have resulted from occupational exposures. No case of herpes B infection has been documented in travellers or others exposed to monkeys in the wild. However, travellers to areas where free-ranging macaques exist should be aware of the potential risk. An infected monkey may appear completely healthy, and herpes B infection rates may be high in some populations. Documented routes of infection include animal bites and scratches, exposure to infected tissue or body fluids, cage scratches, and human-to-human spread. Some exposures resulting in human infection were considered trivial at the time they occurred. Disease may start as an influenza-like illness within 1 month after exposure. Neurologic symptoms develop as the virus infects the central nervous system and may lead to ascending paralysis and respiratory failure. If the disease is untreated, the death rate in humans from herpes B infection reaches 80%. Recent guidelines have been published for the prevention of herpes B infection after exposure and for the treatment of established infection. Travellers should never attempt to feed, pet, or otherwise handle any monkeys.

Poisonous snakes are hazards in many locations, although deaths from snakebites are relatively rare. Snakebites occur in areas where dense human populations coexist with dense snake populations (e.g., Southeast Asia, sub-Saharan Africa, and Tropical America). The Australian brown snake; Russell's viper and cobras in southern Asia; carpet vipers in the Middle East; and coral snakes and rattlesnakes in the Americas are particularly dangerous. Most snakebites are the direct result of startling, handling, or harassing snakes. Because snakes tend to be active at night and in warm weather, as a precaution, travellers should wear boots and long pants when walking outdoors at night in areas possibly inhabited by venomous snakes. Attempts to kill snakes are dangerous. The venom of a small or immature snake can be even more concentrated than that of larger ones; therefore, all snakes should be left alone. Fewer than half of all snakebite wounds actually contain venom, but travellers should be advised to seek immediate medical attention any time a bite wound breaks the skin. Immobilisation of the affected limb and application of a pressure bandage that does not restrict blood flow are recommended first-aid measures while the victim is moved as quickly as possible to a medical facility. Incision of the bite site and tourniquets that impair blood flow to the affected limb are not recommended. Specific therapy for snakebites is controversial and should be left to the judgment of local emergency medical personnel.

The bites and stings of some arthropods may cause unpleasant reactions. Travellers should be advised to seek medical attention if an insect bite or sting causes redness, swelling, bruising, or persistent pain. Those who have a history of severe allergic reactions to insect bites or stings should also consider carrying an epinephrine autoinjector (EpiPen) in case of recurrence. Many insects can transmit communicable diseases, even without the traveller's being aware of the bite. This is particularly true when camping or staying in rustic accommodations. Travellers to many parts of the world should be advised to use insect repellents containing DEET, protective clothing, and mosquito netting. (See Protection Against Mosquitoes and Other Arthropods.) Stings from scorpions can be painful but, with a few exceptions, are seldom dangerous. Stings in infants and children have the highest morbidity and mortality. In general, exposure to scorpion envenomations can be avoided by sleeping under mosquito nets and by shaking clothing and shoes before putting them on.

Bibliography
  • CDC. Dog-bite-related fatalities—United States, 1995-1996. Morbid Mortal Wkly Rep MMWR. 1997;46:463-7.
  • CDC. Nonfatal dog bite-related injuries treated in hospital emergency departments—United States, 2001. Morbid Mortal Wkly Rep MMWR. 2003;52:605-10.
  • Cohen JI, Davenport DS, Sterwart JA, et al; B Virus Working Group. Recommendations for prevention of and therapy for exposure to B virus (Cercopithecine Herpesvirus 1). Clin Infect Dis. 2002;35:1191-203.
  • Gold BS, Dart RC, Barish RA. Bites of venomous snakes. N Engl J Med. 2002;347:347-56.
  • Huff JL, Barry PA. B-virus (Cercopithecine herpesvirus 1) infection in humans and macaques: potential for zoonotic disease. Emerg Infect Dis. 2003;9:246-50.

- Deborah Nicolls and Paul Arguin

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