The US Centers for Disease Control and Prevention said last week it is still investigating a 9 month multistate outbreak of gastroenteritis that has infected over 100 people who most likely caught Salmonella from small pet turtles.

The CDC announced the results of their ongoing epidemiologic and laboratory investigation into the oubreak in the 25th January issue of Morbidity and Mortality Weekly Report (MMWR). The first reported case occurred in May 2007 and the investigation started in October 2007.

The investigation links 103 cases of gastroenteritis in 33 states to Salmonella Paratyphi B var. Java believed to have been caught by being exposed to small turtles.

Most of the patients who were asked, confirmed they had been in contact with a turtle in the seven days leading up to the onset of their symptoms.

Health authorities first noticed the outbreak when they investigated two cases of severe gastroenteritis in teenage girls who had both swum in the same family owned unchlorinated pool at the same time as two small pet turtles.

One of the girls, aged 13, visited a South Carolina hospital emergency department on the 31st August 2007, after experiencing 5 days of bloody diarrhea, abdominal cramps, fever, and vomiting. She was treated but not hospitalized and she recovered 7 days later. A stool specimen was analyzed and shown to contain Salmonella Paratyphi B var. Java.

The other girl, aged 15, was admitted to a hospital in North Carolina with a similar symptom history but she also had acute kidney failure. She spent 8 days in hospital and made a full recovery.

A joint investigation by the two state health departments found that the girls has swum with pet turtles with shells smaller than 4 inches that had been sold illegally in a pet shop in South Carolina.

Tests of the where the turtles were being kept at the pet shop confirmed the same strain of Salmonella Paratyphi B var. Java as that isolated from the younger girl.

Turtles and other reptiles are a well known cause of human Salmonella infection. A study spanning 1967 to 1997 found that 6 per cent of all human laboratory-confirmed, sporadic cases of Salmonella infections in the United States were caused by exposure to reptiles and amphibians. For those under the age of 21 the figure is nearly double, at 11 per cent. A study in New Jersey in 1972 found that small pet turtles accounted for approximately 23 per cent of Salmonella infections in children.

For this reason, the sale and distribution of small turtles with a shell length under 4 inches has been banned in the US since 1975. But in spite of this ban, the public is able to get hold of small turtles from pet shops, flea markets, street vendors, and through the internet, said the CDC.

The North Carolina Department of Public Health (NCDPH) conducted a wider database search of other reports of salmonella infections and found three other people had been infected with Salmonella Paratyphi B var. Java identical to the strain found in the pet shop turtles. And then, following a nationwide request from the NCDPH, other states started reporting the same strain linked to gastroenteritis outbreaks.

This led to a multistate investigation by the CDC and state and local health departments to find out how big this outbreak was nationwide and where the infections were coming from.

The MMWR report from the CDC last week said that as of 18th January 2008, by searching reportable disease databases they have identified 103 cases of human Salmonella infections from this same outbreak strain, in 33 states.

Over half the patients are under 10 years of age and the first patient fell ill in May last year. Of the 80 patients who were asked about contact with turtles, 47 of them said they had been exposed to them in the 7 days leading up to onset of symptoms. No deaths have been reported.

In order to confirm the link with small turtles, the agency carried out a case-control telephone based study during November 15 to December 5 where they asked 70 patients and 45 neighborhood-matched controls about their exposure to turtles, other reptiles, or aquariums containing tropical fish.

Patients who said they had been exposed to turtles answered detailed questions about the type of exposure, for example whether and how they had handled their pets and their habitats. They were also asked about the size, type and source of their pets, and about their awareness of the link between exposure to reptiles and Salmonella infection.

The study revealed that 44 of the 70 patients had reported exposure to a pet turtle before they fell ill, compared with only 2 of the 45 controls.

The patients had come by their turtle in a variety of ways: from pet shops, flea markets, street vendors, as gifts, and one or two said they had either got it through the Internet, from the wild, hatched from an egg given by a relative, or bought it at a conference.

The CDC is still trying to find out if there is one common distributor or farm of origin for the turtles.

Like other reptiles, the majority of turtles carry Salmonella. Small turtles sold as pets are often bred in crowded ponds and nesting areas, which encourages Salmonella. Using antibiotics to try and stop the Salmonella just makes things worse because the bacteria become resistant.

Turtles tend to shed Salmonella when they are stressed, and this makes it very difficult to tell when an animal is free of the bacteria, said the CDC.

“Multistate Outbreak of Human Salmonella Infections Associated with Exposure to Turtles — United States, 2007–2008.”
Morbidity and Mortality Weekly Report (MMWR) published by the CDC on January 25, 2008.
MMWR 57(03);69-72.

Click here for the full report.

Written by: Catharine Paddock