Mojave National Preserve - Diseases

Although diseases are not much of a problem in the desert, there are several that visitors should be aware of. Rabies is a potentially fatal viral disease, usually transmitted through the bite of a rabid animal, which affects the nervous system of humans and other mammals. Tens of thousands of people die of the disease each year in the developing countries of Asia, Africa, and Latin America. Fortunately, human rabies is rare in the United States, with an average of only one or two deaths reported each year. Thousands of people are successfully treated each year after being bitten by an animal that may have rabies. Treatment is extremely effective when administered before symptoms appear, and human fatalities associated with rabies in the United States occur mainly in people who fail to seek medical assistance, usually because they were unaware of their exposure.

All mammal species are susceptible to infection, but in the United States, approximately 90 percent of all reported cases now occur in wildlife, most commonly in raccoons, skunks, foxes, and bats. Any abnormal behavior in wildlife, such as daytime activity of a normally nocturnal species, can serve as a potential indication of rabies, and animals displaying such suspicious behavior should be avoided and reported. In addition, campers should keep all food items and wrappers in their vehicles rather than in their tents since food odors could attract rodents that may be rabid. Although raccoons and skunks are the most frequently reported rabid wildlife species, bats represent the source of most of the recent human rabies cases in the United States. During the 1990s, 74 percent of human rabies cases (24 of 32) were attributed to bat-associated variants of the virus, many of which likely resulted from unrecognized bat bites. For this reason, extreme care should be taken when entering areas, such as caves, that may potentially house bats; a sure sign is the presence of bat droppings, or guano. However, the vast majority of bats are rabies-free and should not be persecuted because of their perceived rabies connection. Bats are important predators, pollinators, and seed dispersers in many of the ecosystems in which they live.

Hantavirus Pulmonary Syndrome (HPS), another potentially fatal viral disease, is an acute respiratory illness caused by several species of hantavirus and transmitted by some rodents. Hantaviruses are a group of viruses found in Asia, Europe, North America, and South America. There are four hantaviruses in the United States that are known to cause HPS, as well as several others which have not been known to cause disease in humans. Hantavirus was first discovered in the United States in 1993, although the earliest known case of HPS occurred in 1959, and Navajo Indian medical belief suggests that there were outbreaks of the disease much earlier than this. As of April 16, 2001, a total of only 283 cases of HPS, with a mortality rate of 38%, have ever been reported in the United States.

The deer mouse ( Peromyscus maniculatus ) carries the most commonly contracted hantavirus, the Sin Nombe virus, in the United States. Other species which are known to carry hantaviruses include the cotton rat ( Sigmodon hispidus ), the rice rat ( Oryzomys palustris ), and the white-footed mouse ( Peromyscus leucopus ). The deer mouse is the only one of these rodent species that occurs in Mojave National Preserve. Although hantavirus may be transmitted from rodent to human directly through a bite, this is very rare. More commonly, people breathe in the virus when rodent droppings, urine, or nesting material that contain the virus are stirred up into the air. It is for this reason that care should be taken when entering a closed space, such as a cave or abandoned mine or cabin, where rodent droppings or nests may be present. Besides being inherently dangerous, if you see mouse droppings you will be at risk for exposure to Hantavirus. In addition, visitors who plan on camping out should select a campsite that is free from rodent droppings.