This article was originally posted on RealClearScience.
A recent issue of the CDC’s Morbidity and Mortality Weekly Report told of two curious cases of infectious disease that were transmitted from animals to humans, also known as zoonotic infections.
The first was a real-life manifestation of the cliché “no good deed goes unpunished.” A truck carrying 350 very young calves overturned in Kansas, killing many of them and injuring others. Fifteen emergency responders arrived to help. A few days later, six of them became severely ill, with diarrhea, cramps, and vomiting. A subsequent epidemiological investigation revealed that they were infected withCryptosporidium, a chlorine-resistant parasite that is transmitted via the fecal-oral route. Emergency responders who either carried injured calves and/or came into contact with feces were far more likely than the other responders to become sick.
Cryptosporidiosis is a rather nasty disease. The diarrhea it causes can last for more than a week. In 1993, Cryptosporidium contaminated the Milwaukee water supply, sickening 403,000 residents and killing 69 of them. The public health disaster prompted The Onion, which was founded in nearby Madison, to create a T-shirt in commemoration.
The second case the CDC described involved a child who was scratched by his pet rat. The child began vomiting and developed a fever. His doctor misdiagnosed him as having viral gastroenteritis, and two days later, he was dead. The subsequent investigation determined that one of his rats carried Streptobacillus moniliformis, the bacterium responsible for “rat-bite fever.”
Oddly, most domesticated rats carry this bacterium, and according to the CDC, 0.1% of U.S. households have pet rats. Why this child became infected and died — while so many other pet rat owners never even become infected — is a bit of a mystery. A quirk of genetics, however, may to be blame. It is known, for instance, that a single mutation can double a person’s chance of catching the flu. Perhaps the child carried a similar mutation that made him susceptible to this particular bacterium.
It should be noted that many of our pets can make us sick. Dog bites can transmitCapnocytophaga, and cats can transmit Bartonella (cat-scratch fever) and Toxoplasma. While our fluffy furballs are cute, always remember that they often possess noxious microbes.
Source: Centers for Disease Control and Prevention. “Outbreak of Cryptosporidiosis Among Responders to a Rollover of a Truck Carrying Calves — Kansas, April 2013.” MMWR 63 (50): 1185-1188.
Source: Centers for Disease Control and Prevention. “Notes from the Field: Fatal Rat-Bite Fever in a Child — San Diego County, California, 2013.” MMWR 63 (50): 1210-1211.