Human Interaction with Animals: A Risk Factor for Injury and Illness
Animals, even those in close association with humans, such as dogs, 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 insects. However, most animals can transmit infection by more than one route. This section provides examples of high-priority diseases and injuries from animals and refers the reader to other sections for more detailed descriptions of the specific diseases.
Bites and scratches
Bites from certain mammals frequently encountered during foreign travel, such as monkeys, dogs, bats, and rodents, can present a risk for serious infection. These animals’ saliva can be so heavily contaminated with pathogens that a bite may not even be necessary to cause infection if saliva enters a preexisting cut or scratch or mucous membrane.
Before departure, travelers should have a current tetanus vaccination or documentation of a booster vaccination in the previous 5–10 years (see Chapter 3, Tetanus). Travel health providers should assess a traveler’s need for preexposure rabies immunization (see Chapter 3, Rabies). While traveling, people should never try to pet, handle, or feed unfamiliar animals (whether domestic or wild, even in captive settings such as game ranches or petting zoos), particularly in areas where rabies is endemic. Young children should be watched closely around unfamiliar animals as they are more likely to be bitten and to sustain more severe injuries from animal bites.
To prevent infection, all bite and scratch wounds should be promptly cleaned with soap and water, and the wound should be promptly debrided by a health care professional if necrotic tissue, dirt, or other foreign materials are 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. Travelers who might have been exposed to rabies should contact a health care provider as soon as possible for advice about rabies postexposure prophylaxis (PEP). Travelers who received their most recent tetanus toxoid–containing vaccine >5 years previously, or who have not received ≥3 doses of tetanus toxoid–containing vaccines, may require a dose of tetanus toxoid–containing vaccine (Tdap, Td, or DTaP).
Dogs and Cats
Although travelers may assume that most dogs and cats are pets and therefore safe to interact with, more rabies cases in humans occur because of bites from free-roaming dogs and cats than from any other animals in the world. Rabies infections in dogs and cats may be difficult to detect, particularly early in the onset of clinical signs. Rabies also cannot be definitively diagnosed in a live animal. Travelers who are bitten or scratched by dogs or cats should promptly clean the wound and seek medical care. To further mitigate the risk of exposure to rabies, unfamiliar dogs should be avoided, and travelers should avoid the temptation to adopt a stray dog from abroad.
Like any other wild animal, bats, whether sick or healthy, may bite if handled. Any suspected or documented bite or scratch from a bat anywhere in the world should be considered a rabies risk, and the traveler should be evaluated for rabies PEP. It is not possible to tell if a bat has rabies without laboratory confirmation; however, any bat that is active by day, is found where bats are not usually seen (for example, indoors or outdoors in areas near humans), or is unable to fly is far more likely to be rabid. People may not know when they have been bitten by a bat, as most bats have tiny teeth, and not all wounds are apparent. Furthermore, because bat bites rarely cause much trauma, people may trivialize the bite and not seek care. Travelers should seek medical advice even in the absence of an obvious bite wound if they wake up to find a bat in the room or see a bat in the room of an unattended child or other person who could not reliably report a bite.
After a monkey bite or scratch, travelers should be advised to thoroughly clean the wound and seek medical care immediately to be evaluated for possible rabies and herpes B PEP. Macaque bites can transmit herpes B virus, a virus related to the herpes simplex viruses (see Chapter 3, B virus). Additional information and photos of macaques can be found at the website for the National B Virus Resource Center at the Georgia State University Viral Immunology Center (www2.gsu.edu/~wwwvir).
Wild rodents are unlikely to have rabies; however, rodent bites and scratches can transmit rat-bite fever, Salmonella , lymphocytic choriomeningitis virus, and monkeypox. Each rodent bite or scratch needs to be evaluated on a case-by-case basis to determine the need for treatment.
Stings and Envenomations
Poisonous snakes are hazards in many locations, although deaths from snakebites are uncommon. 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.
Common sense is the best precaution. Most snakebites result from startling, handling, or harassing snakes. Therefore, all snakes should be left alone. Travelers should be aware of their surroundings, especially at night and during warm weather when snakes tend to be more active. For extra precaution, when practical, travelers should wear heavy, ankle-high or higher boots and long pants when walking outdoors in areas possibly inhabited by venomous snakes.
Travelers should be advised to seek immediate medical attention any time a bite wound breaks the skin or when snake venom is ejected into their eyes or other mucous membranes. Immobilization 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 restrict 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. Specific antivenoms are available for some snakes in some areas, so trying to ascertain the species of snake that bit the victim may be critical.
Insects and Other Arthropods
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 Protection against Mosquitoes, Ticks, & Other Arthropods section earlier in this chapter.
Most marine animals are generally harmless unless threatened. Most injuries are the result of chance encounters or defensive maneuvers. Resulting wounds have many common characteristics: bacterial contamination, foreign bodies, and occasionally venom. Venomous injuries from marine fish and invertebrates are increasing with the popularity of surfing, scuba diving, and snorkeling. Most species responsible for human injuries, including stingrays, jellyfish, stonefish, sea urchins, and scorpionfish, live in tropical coastal waters.
Travelers should be advised to maintain vigilance while engaging in recreational water activities. Prevention is the best defense:
- Avoid contact. This may be difficult in conditions of poor visibility, rough water, currents, and confined areas.
- Do not attempt to feed, handle, tease, or annoy marine animals.
- Wear protective clothing, such as protective footwear.
- Try to find out which animals may be encountered at the destination and learn about their characteristics and habitats before engaging in recreational water activities.
In case of injury, identifying the species involved can help determine the best course of treatment. Signs and symptoms may not appear for hours after contact, or the animal may not have been seen or recognized at the time of injury. In such cases, treatment is based on the injury. Symptoms of venomous injuries can range from mild swelling and redness at the site to more severe symptoms, such as difficulty breathing or swallowing, chest pain, or intense pain at the site of the sting, for which immediate medical treatment should be sought. Management will vary according to the severity of symptoms and can include medications, such as diphenhydramine, steroids, pain medication, and antibiotics.
Travelers should be aware that animals do not have to be sick or appear sick to be a risk to humans. Some animals such as poultry, reptiles, and goats carry human pathogens as normal gut flora. Other animals, such as rodents, bats, and nonhuman primates, can be subclinical carriers of pathogens.
Viral infections such as rabies and viral hemorrhagic fevers can be transmitted from bats to people. Histoplasmosis is a fungal infection that may be associated with bat droppings. Exposure to bats can occur during adventure activities such as caving or spelunking and can include mucosal or cutaneous exposure to bat saliva or droppings, in addition to bites and scratches. A recent example of an indirect exposure is an imported case of Marburg fever in a tourist who had visited a “python cave” inhabited by bats 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.
Bats should never be handled. If a traveler touches a bat or if infectious material (such as saliva) from a bat gets into the eyes, nose, mouth, or a wound, the traveler should wash the affected area thoroughly and seek medical advice immediately. Travelers should be discouraged from going into caves or mines that have bat infestations. If travelers will be entering densely populated bat habitats, they should wear protective equipment and clothing (face shield, respirator, gloves). Dirty clothing should be removed and washed as soon as possible after leaving the cave. If travelers, particularly adventure travelers, know they will entering high-density bat habitats or plan on having direct contact with bats or other rabies reservoir species, preexposure rabies vaccination should be considered.
Rodents carry a variety of viral, bacterial, and parasitic agents that may pose a threat to human health. Human exposure can occur directly by a bite or scratch or indirectly by exposure to surfaces or water contaminated with urine or feces. Rodents can also be reservoirs for vectorborne infections carried by fleas, ticks, and mites.
Wild rodents should never be handled. Travelers should avoid places that have evidence of rodent infestation and should avoid contact with rodent feces. Travelers should not eat or drink anything that is suspected to be contaminated by rodent feces or urine.
Travelers who were exposed to rodents or who have a history of flea or tick bites or mite infestation may develop febrile illness shortly after exposure and should be evaluated by a clinician. Depending on the history and symptoms, diseases such as plague, leptospirosis, hantavirus, rickettsial infections, Lyme disease, lymphocytic choriomeningitis, Lassa fever, tickborne encephalitis, poxvirus, tularemia, and bartonellosis (see Chapter 3) should be included in the list of possible diagnoses.
Both ill and asymptomatic birds have been associated with cases of highly pathogenic avian influenza in humans. When traveling in an area where outbreaks of avian influenza have been reported, travelers should avoid contact with live poultry (such as chickens, ducks, geese, pigeons, turkeys, and quail) or any wild birds and should avoid settings where avian influenza A (H5N1 or H7N9)–infected poultry may be present, such as commercial or backyard poultry farms and live poultry markets. Other pathogens from birds may infect humans through infected feces or by aerosol. These cause diseases such as histoplasmosis (see Chapter 3, Histoplasmosis), salmonellosis (see Chapter 3, Salmonellosis [Nontyphoidal]), psittacosis, and avian mycobacteriosis.
Travelers should not eat uncooked or undercooked poultry or poultry products, including dishes that contain uncooked eggs or poultry blood. Travelers should wash their hands if they come in contact with bird feces.
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Heather Bair-Brake, Ryan M. Wallace, G. Gale Galland, Nina Marano