Infections of Leisure, Fourth Edition

Venturing into wilderness environments can be exhilarating, and each year millions of people take time off to enjoy the pastime. During this relaxing endeavor, the majority of adventurers come into contact with different species of biting arthropods. Ticks, mosquitoes, lice, fleas, mites, bees, wasps, scorpions, and spiders can make time spent outdoors unpleasant, and they are potential carriers of disease. The major diseases in the United States which are transmitted to humans by ticks include Lyme disease, human monocytic ehrlichiosis (HME), human granulocytic anaplasmosis (HGA), Rocky Mountain spotted fever (RMSF), and tularemia. The major manifestation of the first stage of the disease (early, localized infection) is the localized skin rash termed erythema migrans, which is present in up to 80% of patients. The majority of reported cases, however, are from the southeastern part of the United States, with approximately 80% of reported cases occurring during the months of May and June. In the western United States, wood ticks (Dermacentor andersoni) are the primary carriers and vectors of infection, whereas the dog tick (Dermacentor variabilis) and the Lone Star tick (Amblyomma americanum) represent the most common arthropod hosts in the eastern United States and the south-central region, respectively. A proper wardrobe is essential in preventing tick-transmitted diseases. Permethrin can be sprayed on clothing to prevent tick attachment, and insect repellents that employ N,N-diethyl-3- methylbenzamide (DEET) can be applied to the skin for further protection.

The relationship between humans and dogs is an ancient one. The dog has been our workmate, protector, guide, and companion. 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 chapter. Bacterial zoonoses transmissible from dogs to human beings include campylobacteriosis, salmonellosis, leptospirosis, and brucellosis. Campylobacteriosis is found throughout the world and is an important cause of human bacterial diarrhea, being as common as or more common than salmonellosis and shigellosis. The common clinical presentation of canine salmonellosis consists of fever, vomiting, and diarrhea (varying from watery to mucoid to bloody). The most severe form of leptospirosis, known as Weil's disease, is characterized by hepatic and renal dysfunction, hemorrhage, and circulatory collapse. The clinical manifestations of human toxocariasis are classified as visceral larva migrans (VLM), ocular larva migrans, and neurological toxocariasis. Children exposed to dogs treated for roundworm infection are less likely to have positive serologic tests for Toxocara canis than children exposed to untreated dogs. Other preventive measures include removing children with pica from environments thought to be contaminated, prohibiting canine access to children's game areas, and frequently turning over sand in public parks. The majority of human infections with Echinococcus granulosus are asymptomatic. The disease is indolent, as cysts enlarge slowly over many years. The growing cysts may remain unilocular or become multilocular with the formation of daughter cysts.

Infectious diseases can be transmitted to humans from birds by one of several mechanisms. In group 1 infections, birds are the natural reservoirs for the infectious agent, which causes illness among them. 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. Psittacosis is mainly an occupational disease among workers in turkey-processing plants, duck or goose pluckers, pigeon breeders, and pet store employees. Mites that infest wild and domestic birds have four stages (egg, larva, nymph, and adult) in their life cycles, which can be completed within 1 week under favorable circumstances. Gastrointestinal defenses may be compromised by antacids, gastrectomy, agents that slow intestinal motility, and antibiotics. Some diseases, such as cirrhosis, lymphoma, and human immunodeficiency virus (HIV) infection, which impair systemic host defenses, also increase susceptibility to salmonellosis. Acute pulmonary histoplasmosis resembles atypical pneumonia, the severity of which depends on the number of infectious particles inhaled.

This chapter highlights the zoonotic diseases of rats, and in certain cases the same diseases in other rodents, which have clinical relevance in the United States and its territories. In an attempt to feed more often because of the blockage, the flea ingests the host's blood into its esophagus, where it mixes with yersiniae growing in this location and in the proventriculus. Aminoglycosides such as streptomycin and gentamicin are the most effective antibiotics in vivo against Yersinia pestis. Rarely, the patient presents with uveitis, myocarditis, cranial nerve palsy, or the Jarisch-Herxheimer reaction, which is attributed to decreasing bacterial numbers in the patient's blood and a massive cytokine release and occurs during initial treatment of the spirochetal infection with an effective antibiotic. As with other microbial infections, the disease's severity relates to the organism's serotype, the number of bacteria ingested, and the host's susceptibility. In a retrospective study of 23 patients with Helicobacter cinaedi-associated illness, 22 of the cases had the organism isolated from blood by an automated blood culture system, with which a slightly elevated growth index was noted. This study also described a new H. cinaedi-associated syndrome consisting of bacteremia and fever and accompanied by leukocytosis and thrombocytopenia. The major clinical difference between monkeypox and smallpox is the pronounced lymphadenopathy noted in the majority of patients infected with monkeypox virus.

There are several mechanisms by which infectious agents may be spread during sports. The main routes of transmission include direct- and indirect-contact, droplet, common-source, and airborne transmission. Common etiologies of sports-related infections are discussed in this chapter. Transmission resulting from nonathletic bloody fistfights has been reported. Herpes simplex virus (HSV) is the cause of a contagious viral infection of the skin and mucous membranes. Upper respiratory tract infections (URI), which are caused by a number of viruses and bacteria, are some of the most common illnesses encountered in sports. Athletes participating in water sports may be at risk, depending on the type of activity and water quality. Leptospirosis and otitis externa, two of the prominent water-based diseases faced by athletes, are discussed. Acute otitis externa, also known as swimmer’s ear, is an inflammation of the external auditory canal. It is typically seen among athletes participating in water sports who commonly experience mechanical trauma to the external ear. Common-source exposure to infectious diseases in athletic settings normally occurs in cases where water or food containers are contaminated and shared. Vector-borne pathogens are spread by carriers such as ticks, insects, or animals. To avoid the spread of fungal infections of the feet, athletes should wear proper footwear, keep the feet and socks dry during sporting activities, and avoid going barefoot in shared areas, such as the locker room and shower.

This chapter reviews the clinical syndromes and epidemiology of the most commonly encountered sexually transmitted infections (STIs), as well as the clinical and behavioral aspects of travel and sexually transmitted disease (STD) epidemiology. Long-term travelers such as expatriates are at increased risk for human immunodeficiency virus (HIV) and STIs. Sexual intercourse with commercial sex workers (CSWs) is very common among travelers, expatriates, and military personnel and is one of the major risk factors for HIV and other STDs. A study of Hong Kong residents found that condom use was higher when they used CSWs in Hong Kong (91%) than when they used CSWs from mainland China (66%) and that self-reported STD rates were four times higher in those who had traveled to the mainland, 33% of travelers to the mainland had used services of CSWs, and 11% had used these services on the most recent trip. Several review papers have addressed special problems facing HIV-infected travelers. A major concern for all HIV-infected travelers is the risk for opportunistic infections. Persons who are sexually active with multiple partners should have periodic screening for STDs, especially gonorrhea, chlamydia, syphilis, and HIV, at least on an annual basis.

Many host and environmental factors enhance susceptibility to infectious diseases, such as altered immune responses, hypoxia, physiological adaptation or lack of such adaptation, environmental stressors, increased UV radiation, cramped quarters, inability to maintain personal hygiene, and isolation from adequate medical care. The risk of contracting an infection varies depending on location, length of exposure, and nature of the high-altitude activity. There are few published data on this topic, and as a result, portions of this chapter are anecdotal and based on personal medical experience. Cysticercosis of the brain is one of the most common causes of epilepsy in Nepal. Respiratory problems are common at high altitudes. Arthropod-borne infections are extremely common in travel to developing countries, but arthropod vectors are less common at higher altitudes. Sexually transmitted diseases, fungal vaginitis, and urinary tract infections are usually present in typical fashion at high altitude. Physicians counseling patients who travel with cancer, human immunodeficiency virus, chronic steroid or other immunosuppressive medication use, functional or anatomic asplenia, and renal insufficiency should familiarize themselves and their patients with the travel risks associated with these conditions. The differential diagnosis of illness at high altitude includes other conditions that may be misdiagnosed as an infection. Physicians who may treat infectious diseases at high altitude should carry appropriate chemotherapy and supportive equipment. In essence, infections and infectious diseases at high altitude often parallel those in adjacent lowland environments.

There are many considerations in evaluating perils associated with the wide range of venues where animal contact can occur. First, many venues or events draw large numbers of people; some operate during a short time frame, while others, such as zoos and aquariums, operate year-round. Second, petting zoos and other animal contact venues are particularly popular with children, who are likely to have less stringent hygiene and are more susceptible to severe disease outcomes. Finally, there is remarkable variability in the physical layout of venues that permit animal contact and in the types of animals that may be contacted. Perils of animal contact include allergies, injury, and zoonotic disease transmission. Potential zoonotic pathogens in petting zoo venues are discussed in this chapter. The Centers for Disease Control and Prevention (CDC) first published recommendations to reduce perils associated with petting zoos following an outbreak of human Escherichia coli O157 infections associated with animal contact in 2000. The petting zoo associated with the outbreak was one of many exhibits where the public could contact animals. Hand washing is the single most important preventive measure to minimize infectious disease perils of the petting zoo. One practical tip is to educate the public to recognize zoonotic disease perils of the petting zoo.

Many foods, such as seafood or dairy products, are preferentially eaten raw or unpasteurized in their most fresh and tasty form. This maximizes their potential to act as vectors for bacteria, viruses, and parasites. Some of these pathogens are well known to clinicians; others cause rare zoonoses that do not normally infect humans and may escape early recognition, and some may in fact cause newly emerging diseases. Alas, even cooked food can transmit prions, leading to diseases such as kuru, but since the ingestion of human brains is now rare, in this chapter the author focuses on more likely or exotic diseases. The capture or slaughter of some animals for food can also be risky. The recent pandemic of severe acute respiratory syndrome (SARS) caused by a coronavirus is illustrative. Wild game meat is now the most common source of infection, with transmission from bears, cougars, and boars being well documented. In individuals with AIDS, the most common manifestation of toxoplasmosis is recrudescent disease of the brain from old, formerly silent cysts. Central nervous system (CNS) toxoplasmosis is the most common CNS opportunistic infection in AIDS patients in the developed world. There is evidence that treatment of pregnant women with acute toxoplasmosis leads to reduced risk of disease in the fetus.