water hog: see capybara.

hog cholera, acute, highly infectious viral disease of swine, also called swine fever. It is perhaps the most serious disease of swine in North America. It is characterized by dullness and listlessness, loss of appetite, rise in temperature to between 105°F; (41°C;) and 107°F; (42°C;), diarrhea, and often death. Purple hemorrhagic areas will appear on the abdomen and many pigs display nervous signs, such as circling, incoordination, muscle tremors, and convulsions. Mortality is very high and recovered animals are permanently stunted. The disease is transmitted readily by direct or indirect contact. The virus may enter a herd through contaminated feed, water, equipment, or by contact with an infected animal or person. At one time, feeding pigs raw garbage containing pork scraps from infected pigs was a common cause of infection. For this reason the United States and many other countries now prohibit the feeding of uncooked garbage to pigs. A national hog cholera eradication program has been established in the United States to eliminate all possible sources of virus introduction. A vaccine is available in areas where the disease is still present.

hog: see swine.

Semiaquatic rodent (Hydrochoerus hyrdrochaeris) of Central and South America. Classified as the only species in its family, it is related to the cavy and the guinea pig. Capybaras are the largest living rodents, growing as large as 50 in. (1.25 m) long and weighing 110 lbs (50 kg) or more. They are sparsely haired and brownish, with a blunt snout, short legs, small ears, and almost no tail. Capybaras are shy and associate in groups along the banks of lakes and rivers. Herbivorous, they can become pests when they eat cultivated melons, grain, and squash. They swim and dive readily and commonly enter water to elude predators.

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or swine fever

Often fatal viral disease of swine in Europe, North America, and Africa, transmitted by vehicles used to carry pigs, people dealing with them, and uncooked garbage in feed. Fever progresses to symptoms that include appetite loss; affected eyes and digestive tract; respiratory difficulty; rash; and inflamed mouth and throat. The pig moves reluctantly and staggers; later it cannot rise; coma follows. Antiserum is rarely effective. Survivors become chronically ill and can spread the virus. Illness must be reported, infected animals slaughtered, and quarantine instituted. A vaccine can control it. The African strain causes death sooner and has no effective prevention or treatment.

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in full polychlorinated biphenyl

Any of a class of highly stable organic compounds prepared by the reaction of chlorine with biphenyl, a two-ring compound. The commercial product, a mix of several PCB isomers, is a colourless, viscous liquid that is almost insoluble in water, does not degrade under high temperatures, and is a good electrical insulator (see dielectric). PCBs became widely used as lubricants, heat-transfer fluids, and fire-resistant dielectric fluids in transformers and capacitors in the 1930s and '40s. In the mid 1970s they were found to cause liver dysfunction in humans and came under suspicion as carcinogens; their manufacture and use were consequently restricted in the U.S. and many other countries, though illegal dumping by manufacturers continued. They persist in the environment and have entered the food chain, causing great harm especially to invertebrates and fish.

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