Chapter 3 Environmental Hazards & Other Noninfectious Health Risks
Animal Bites & Stings (Zoonotic Exposures)
INJURY & ILLNESS
Animals do not have to be sick to be a risk to humans. Animals such as poultry, reptiles, and goats, carry human pathogens as normal flora. Other animals, such as rodents, bats, and nonhuman primates, can be subclinical carriers of pathogens. Animals, even those in close association with humans, such as dogs or animals in petting zoos, can attack if they feel threatened, are protecting their young or territory, or are injured or ill.
Travelers should be aware that attacks by domestic animals are far more common than attacks by wildlife, and secondary infections of wounds may result in serious illness or death. This section will cover the most common routes of transmission of illness and injury from animals and will highlight those animals that are common reservoirs of zoonotic diseases (Table 3-03). See the respective disease sections in Chapter 4 for more detailed information on specific diseases.
ROUTES OF TRANSMISSION
Bites and Scratches
Bites from certain mammals encountered during foreign travel (monkeys, dogs, bats, and rodents) present a risk for serious infection. Saliva from these animals can be contaminated so heavily with pathogens that a bite may not be required to cause human infection; contact with a preexisting cut or scratch or mucous membrane can represent sufficient exposure.
Before departure, travelers should have a current tetanus vaccination or documentation of a booster vaccination in the previous 5–10 years (see Chapter 4, Tetanus). Travel health providers should also assess a traveler’s need for preexposure rabies immunization (see Chapter 4, Rabies). During travel, people should never try to pet, handle, or feed unfamiliar animals (domestic or wild, even in captive settings such as game ranches or petting zoos), particularly in areas where rabies is enzootic. Avoiding unfamiliar animals can help mitigate the risk of exposure to rabies, and travelers should avoid the temptation to adopt stray animals from abroad. Advise parents traveling with young children to watch them carefully around unfamiliar animals, as they are more likely to be bitten or scratched and to sustain more severe injuries.
Travelers should clean all bite and scratch wounds quickly with soap and water to prevent infection. Wounds contaminated by necrotic tissue, dirt, or other foreign materials should be debrided promptly by health care professionals, if present. Often, a course of antibiotics is appropriate after dog or cat bites or scratches, as these can lead to local or systemic infections.
Wound care is especially important for exposures where rabies or tetanus is a concern. Health care professionals should evaluate travelers bitten or scratched by any animal, but particularly if the attack was unprovoked, to assess the need for rabies postexposure prophylaxis (PEP). In many countries dogs, terrestrial carnivores, and bats are the most commonly reported rabid animals; a health care professional should treat high-risk exposure immediately.
Rabies is comparatively rare in primates and rodents. Nevertheless, travelers should seek evaluation from a health care professional, especially if an attack was unprovoked or the animal appeared ill. Additionally, if bitten or scratched by a monkey, travelers should be evaluated for B virus PEP (see Chapter 4, B Virus).
Travelers with high-risk exposures (including animal bites and scratches) not vaccinated for tetanus will require a dose of tetanus toxoid–containing vaccine (Tdap, Td, or DTaP). This applies to those who received their most recent tetanus toxoid–containing vaccine >5 years before their exposure and those who have not received ≥3 doses of tetanus toxoid–containing vaccines.
Stings and Envenomations
Snakes, insects, and marine fish and invertebrates are hazards in many locations. Snakebites usually occur in areas where dense human populations coexist with dense snake populations, such as Southeast Asia, sub-Saharan Africa, and tropical areas in the Americas; 25%–40% of venomous snakebites result in negligible or trivial envenomation.
Bites and stings from spiders and scorpions can be painful and can result in illness and death, particularly among infants and children. Other insects and arthropods, such as mosquitoes and ticks, can transmit infections (see the Mosquitoes, Ticks & Other Arthropods section in this chapter).
Most injuries from marine fish and invertebrates occur from chance encounters or defensive maneuvers. Resulting wounds have many common characteristics: bacterial contamination, foreign bodies, and occasionally venom. The incidence of venomous injuries from marine fish and invertebrates is rising as the popularity of surfing, scuba diving, and snorkeling increases. Most species responsible for human injuries, including stingrays, jellyfish, stonefish, sea urchins, and scorpionfish, live in tropical coastal waters.
Avoiding stinging and venomous animals is a traveler’s best precaution. Most stings and envenomation result from startling, stepping on, handling, attempting to feed, or otherwise harassing the animal.
- Before engaging in recreational activities, travelers should try to learn about the animals they may encounter, including their characteristics and habitats.
- Travelers should be aware of their surroundings:
- Especially at night and during warm weather when snakes tend to be more active
- When water conditions create poor visibility, rough water, currents, or confined areas
- Travelers should wear protective clothing:
- Heavy, ankle-high or higher boots and long sleeves and pants when walking outdoors in areas possibly inhabited by venomous snakes and biting insects
- Rash guards, swim boots, or other protective footwear in water where these animals are present
- See Mosquitoes, Ticks & Other Arthropods section in this chapter for information on proper insect repellent use.
Advise travelers to seek immediate medical attention any time a sting or envenomation occurs. In case of injury, species identification can help direct the best course of treatment. Photographs of the animal can aid medical personnel. Immobilization of affected limbs and application of pressure bandages that do not restrict blood flow are recommended first aid measures during victim transport to a medical facility.
Incision at bite sites and use of tourniquets to restrict blood flow to affected extremities should not be used as therapeutic options. Snakebite care is controversial and should be left to local emergency medical personnel. Specific antivenoms are available for some snakes in some areas; knowing the species of snake involved may prove critical to management. Consultation with a herpetologist can be beneficial.
If the traveler does not see or recognize the animal, health care providers will need to base treatment on the nature of the injury and the clinical effects. Bear in mind that—in some cases, at least—signs and symptoms may not appear for hours after contact. Symptoms can range from localized mild swelling and redness to more severe findings, such as difficulty breathing or swallowing, chest pain, or intense pain at the sting or bite site. Management will vary according to the severity of symptoms; therapy may include diphenhydramine, steroids, pain medication, and antibiotics.
Inhalation and Ingestion
The normal flora in the saliva, urine, and feces of many animals are pathogenic for humans. However, exposure to animal body fluids is not always obvious or recognized. For example, water contaminated with animal urine or feces may be used to wash food items.
Discourage travelers from going into caves, tunnels, or mines housing large populations of animals. Travelers planning to enter densely populated animal habitats (such as bat caves) should don protective equipment (face shield, respirator, gloves) and clothing. Upon leaving, they should then doff dirty equipment and clothing and wash or bathe as soon as possible. Travelers should not eat or drink anything potentially contaminated by animal feces or urine. Avoiding dusty animal enclosures or housing can help prevent the inhaling of aerosolized urine and/or feces.
Illness related to animal excreta may not appear for hours or even weeks after exposure. Health care providers must take highly detailed travel histories that include all activities resulting in exposure to or contact with animals and their habitats. Base treatment of illness on signs, symptoms, and the specific pathogen.
Table 3-03. Common reservoirs of zoonotic diseases and mechanisms/routes of human infection
|ANIMAL RESERVOIR||DISEASES TRANSMITTED BY MECHANISM/ ROUTE OF INFECTION||RECOMMENDATIONS FOR TRAVELERS|
|BITES & SCRATCHES||INHALATION & INGESTION|
|Rodents||Rodent bites and scratches can transmit rat- bite fever, lymphocytic choriomeningitis virus, viral hemorrhagic fevers, monkeypox, and many other zoonotic pathogens.||
||Avoid places with evidence of rodent infestation.|
1A recent example of an indirect exposure is an imported case of Marburg fever in a tourist who had visited a cave inhabited by bats (Python Cave in western Uganda). This case illustrates the risk of acquiring diseases from indirect contact with cave- dwelling bats. This same cave was the source of a fatal case of Marburg hemorrhagic fever in a Dutch tourist in 2008.
- Callahan M. Bites, stings and envenoming injuries. In: Keystone JS, Freedman DO, Kozarsky PE, Connor BA, Nothdurft HD, editors. Travel Medicine. 3rd ed. Philadelphia: Saunders Elsevier; 2013. pp. 413–24.
- Cohen JI, Davenport DS, Stewart JA, et al. Recommendations for prevention of and therapy for exposure to B virus (cercopithecine herpesvirus 1). Clin Infect Dis. 2002 Nov 15; 35(10):1191–203.
- Daly RF, House J, Stanek D, Stobierski MG. Compendium of measures to prevent disease associated with animals in public settings. J Am Vet Med Assoc. 2017; 251(11):1268–92.
- Diaz JH. The global epidemiology, syndromic classification, management, and prevention of spider bites. Am J Trop Med Hyg. 2004; 71(2):239–50.
- Gibbons RV. Cryptogenic rabies, bats, and the question of aerosol transmission. Ann Emerg Med. 2002; 39(5):528–36.
- Han BA, Kramer AM, Drake JM. Global patterns of zoonotic disease in mammals. Trends Parasitol. 2016; 32(7):565–77.
- Hifumi T, Sakai A, Kondo Y, Yamamoto A, Morine N, Ato M, et al. Venomous snake bites: clinical diagnosis and treatment. J Intensive Care. 2015; 3(16):1–9.
- Lankau EW, Cohen NJ, Jentes ES, Adams LE, Bell TR, Blanton JD, et al. Prevention and control of rabies in an age of global travel: a review of travel- and trade-associated rabies events—United States, 1986–2012. Zoonoses Public Health. 2014; 61(5):305–16.
- Meerburg BG, Singleton GR, Kijlstra A. Rodent-borne diseases and their risks for public health. Crit Rev Microbiol. 2009; 35(3):221–70.
- World Health Organization. WHO Expert Consultation on rabies, Second report. World Health Organ Tech Rep Ser. 2013; 982:1–139.