Many people enjoy cuddling their pets. They should be aware, however, that they risk infecting themselves with an illness, be the object of their affection a dog, a cat or an exotic variety of snake.
"Pet owners ought to know that pets can definitely be hazardous," says Klaus Osterrieder, managing director of the department of veterinary medicine at the Institute of Virology at Berlin's Free University.
Although zoonoses - infectious diseases transmissible from vertebrate animals to humans - are much more frequent in livestock, pets can also be a source of infection.
One possible problem is a fungal skin infection. Particularly in rural areas, dogs and cats can become infected by livestock and then pass the fungus on to people, explains Professor Ingo Nolte of the University of Veterinary Medicine in Hanover.
A pet with a fungal skin infection is easily recognizable. "Round bald spots in its fur are a symptom," notes Nolte, who says the ailment is easily treatable and not serious.
Fleas are not serious either, but they are a big nuisance. "Cat fleas are the most common," Nolte remarks. Dogs can transmit mite infections, such as pseudoscabies, which, Nolte says, results in itching and reddened skin that "lasts a few days and then usually goes away by itself".
Cats also occasionally transmit cat scratch fever, a bacterial disease. "Localized pustules appear," Osterrieder says. In rare cases, the pustules spread over the entire body. A problem, he says, is that many pet owners and physicians do not immediately recognize the cause of the ailment.
Animals sometimes pass on viruses like cowpox, as happened in 2008 in the German states of North Rhine-Westphalia and Bavaria. "Most of the people affected had kept infected rodents such as colored rats, or had fed them to their snakes," Osterrieder says.
"In humans, this pox occurs after they've handled the animal, and it's usually confined to the lips or eyes. But it can spread to the entire body of people with weakened immune systems, and even lead to death."
Snakes and other reptiles are not wholly harmless either. Domestically bred animals are generally unproblematic, according to Rudolf Hoffmann, a veterinarian specializing in fish and reptiles who works at Munich's Reptile Collection Station.
"Animals recently imported from the tropics, in particular, could be infected, however," he says.
Snakes, for example, can carry one-celled parasites. The infection usually becomes evident to their owners when the animals vomit.
"Cleaning a terrarium can lead to a faecal smear infection with major gastrointestinal consequences," Hoffmann points out. Salmonella can also be transmitted in this way.
"Keeping reptiles is not really risky when proper hygiene is observed, however," he adds. This meant not taking animals like turtles into bed, and washing one's hands thoroughly after handling them.
No matter what kind of pet they have, owners should not be overly worried about infection. "Theoretically, pets can transmit just about everything, from viruses to bacteria to parasites," Osterrieder says. "In practice, though, it happens amazingly seldom."