Infections of Leisure, Fifth Edition

Arthropods are the invertebrate phylum that includes both the eight-legged arachnids (ticks, mites, and spiders) and the six-legged insects (mosquitoes, ants, bees, and wasps). Leisure-time activity frequently brings people in contact with these pests, so bites and stings are often part of the price paid for outdoor fun. Most bites and stings are simply painful nuisances that resolve without treatment. Unfortunately, some arthropods, most notably ticks, pose the risk of transmitting serious infectious diseases such as Lyme disease (Borrelia) and rickettsial infections. This article will focus primarily on North American tick-borne diseases and syndromes. In the tropics, mosquitoes and other arthropods are a major source of disease transmission, but a few mosquito and other arthropod-borne North American diseases (e.g., babesiosis and West Nile disease) also merit discussion. Climate change and global transportation have the potential to change disease patterns, and many so-called tropical diseases are moving north or appearing in new areas.

The relationship between humans and dogs is an ancient one. Dogs have been our workmates, protectors, guides, and companions. No one would question the merit of the long history of valuable service that dogs have provided to humans; it is the stuff of legend and literature. We even have evidence that a dog companion may be good for our physical health given that contact with dogs has been shown to lower blood pressure, ameliorate depression, and produce a survival benefit after myocardial infarction. Occasionally, however, pathogens may be transmitted from dogs to human beings, resulting in problems ranging from a trivial rash to life-threatening bacteremia. These infections are reviewed in this article.

Infectious diseases can be transmitted to humans from birds by one of several mechanisms ( Table 1 ). In group 1 infections, birds are the natural reservoirs for the infectious agent, which causes illness among them. The diseased birds then disseminate the infectious agent into the environment, and humans become infected as accidental hosts. Examples of such infections include psittacosis, Newcastle disease, avian influenza, and yersiniosis. In group 2 and 3 infections, birds are the natural reservoirs for the infectious agent but do not become ill themselves. The infectious agents of group 2 infections (for example, salmonellosis and mite infections) disseminate from the colonized birds into the environment directly, and the agents of group 3 infections (for example, eastern equine encephalitis [EEE], western equine encephalitis [WEE], St. Louis encephalitis [SLE], and Japanese B encephalitis [JE]) disseminate by means of arthropod vectors and involve humans as accidental hosts. With group 4 infections, birds are not the natural reservoirs, but they facilitate growth of the organisms in the environment by means of their fecal matter. Examples of infections of the last category include the fungal diseases histoplasmosis and cryptococcosis.

Numerous methods have been used by countless countries attempting to eradicate the rat, but it continues to successfully colonize both urban and rural settings on a global level. One novel approach first introduced in Asia and Europe and then in the United States was the use of domestic ferrets for rodent control.

Rabies is one of the oldest recognized zoonotic diseases. The first recorded description of canine rabies was apparently made by Democritus around 500 B.C.E. Aristotle, writing of rabies in his Natural History of Animals, described dogs suffering from a madness causing irritability and noted that other animals became diseased after being bitten by these sick dogs. Little has changed with this human-carnivore dynamic since the time of Aristotle’s observations. In most areas of the world where the disease is enzootic, dogs and other carnivores remain the predominant sources of human rabies virus infection. For the lucky few that live in countries where canine rabies has been eliminated, the epidemiology of human rabies continues to implicate bats as an important emerging rabies reservoir. Bats are also the focus of ongoing discovery of new lyssaviruses (15 total recognized or putative species), many of which are still poorly understood.

International tourist arrivals surpassed 1 billion by 2012 and continue to increase. In 2013, nearly 24 million U.S. residents traveled abroad for leisure or to visit friends and relatives (http://travel.trade.gov/outreachpages/outbound.general_information.outbound_overview.html). Of these travelers, 35% went to Europe, 27% to the Caribbean, 17% to Asia, 7% each to South America and Central America, 6% to the Middle East, and under 3% to Africa.

Tattoos and body piercing have received more attention from the medical community in recent years. The increasing acceptance of tattoo and body piercing culture by mainstream society is evidenced by the popularity of numerous reality television shows, particularly those focused on tattooing. Temporary tattoos and body jewelry (without actual piercing) are popular decorative items for children as well. The term “body modification” or “body art” has been used to describe procedures that “enhance” a person’s appearance, whether permanent or temporary. These procedures include tattooing, body piercing, scarification, branding, and surgical modifications. For many people, body modification represents a form of artistic or creative expression that provides long-term enjoyment and thus can be considered a recreational pursuit. A positive effect of the increased interest in tattoos and body piercing has been the development of standardized protocols of infection control to protect the health and safety of both the client and the tattooist or piercer. Though the incidence of serious postprocedure complications appears to be low, a significant number of tattoos and body piercings are still performed by personnel who often do not follow appropriate precautions, thus increasing the possibility of both infectious and noninfectious complications.

The air provided to passengers and crew on commercial jet aircraft is typically a combination of conditioned external (ambient) air that has been diverted to the cabin from the engine compressor stages, and air that is taken from the cabin, filtered, and recirculated. The first filter of recirculated air traps the largest particles. Then, on most modern aircrafts, the air passes through high-efficiency particular air (HEPA) filters before reentering the passenger cabin. The most efficient HEPA filters capture 99.97% of particles between 0.1 and 0.3 micrometer and 100% of the larger particles. In addition, the ultra-small contagion also gets captured by Brownian and electrostatic forces. The environmental control system is designed to minimize the introduction of harmful contaminants into the cabin and to control cabin pressure, ventilation, and temperature. Most commercial aircraft provide 10 to 15 air changes per hour of the passenger cabin depending upon the aircraft type, as the original cabin air is progressively diluted with incoming ambient air. Cabin airflow is principally side to side and compartmentalized into four- to seven-seat rows within the passenger cabin, thereby limiting longitudinal (front to back and vice versa) cabin contamination. However, although the principle is side-to-side airflow, evidence employing computational fluid dynamic modeling in a mockup full-sized aircraft cabin section suggests that airflow patterns can be influenced by many factors including seat and cabin geometry, occupancy density, and thermal loads of passengers and equipment.

“Exotic” food dishes reflect the diversity of human culture. From raw turtle eggs and raw snake meat in Asia, crocodile meat in Australia, and raw duck blood soup in Vietnam, examples abound of food considered exotic to those from other areas of the world. With the increase in international travel to remote areas of the world, globalization of the food supply, and changes in food habits, more people are consuming dishes once considered exotic. Many such individuals are immunosuppressed or susceptible to infection based on underlying medical conditions (e.g., HIV) or age and expose themselves to potentially risky food for the purposes of cultural exploration and adventure. Despite improvements in hygiene, water purification, and food sanitation in some locales, many parts of the world continue to be plagued by deficiencies in these areas.