Question

An outbreak of this disease, an illness with high mortality, was observed in captured wild prairie dogs at a commercial exotic animal distributor in Texas. Before shipments were halted on 1 August 2002, approximately 250 of an estimated 3,600 prairie dogs that passed through the Texas facility had died. The sick animals were believed to be part of a single shipment of prairie dogs that were caught in South Dakota starting on 18 May and shipped to the Texas distributor 16 June. Prairie dogs were shipped by the Texas facility and by a South Dakota trader to wholesalers, retailers, and individuals in Arkansas, Florida, Illinois, Michigan, Mississippi, Nevada, Ohio, Texas, Washington, and West Virginia and exported to Belgium, the Czech Republic, Japan, The Netherlands, and Thailand. Unusually high numbers of sick or dead prairie dogs were reported from Texans and the Czech Republic.

There were some reports of human illness following handling of prairie dogs. After 2 to 6 days, individuals experienced a sudden onset of a high fever, chills, headaches, and muscle aches, and a feeling of weakness. In addition, chest discomfort and a dry cough were common.

The CDC laboratory tests of blood and sputa revealed the bacterium, a small, aerobic, gram-negative coccobacillus, also seen in rabbits (which gives this disease its nickname). Identification was completed in a specialized high-level biosafety laboratory.

Due to the potential for global outbreak, the World Health Organization and the European Union Disease Surveillance Network became involved in the investigation. This organism is also a potential bioweapon and is among the CDC’s top six agents of concern. This outbreak was not a bioterrorist attack.

1. What disease was seen in the prairie dogs?
2. What is the name of the etiological agent?
3. How would the people infected be treated for this disease?
4. Is there a way to prevent this for people who are at risk of contracting it?
5. What arthropod can spread this disease?

Answer 1

1. The disease was Tularemia. This disease is cause by a bacterium. The incubation period is typically 2-6 days, although it can vary between 1-14 days. The disease initially starts with high fever, chills, muscle pain, dry cough and fatigue. Skin infection result in rashes with regional lymphadenopathy. Mode of infection in humans is by handling wild rabbits or tick/fly bites. It can also be transmitted by drinking contaminated water. It can be of different types- ulceroglandular, glandular, oculoglandular, oropharyngeal, pneumonic or typhoidal.

2. The etiological agent is Francisella tularensis. It is one of the deadliest bacteria known as inhalation of as few as 10 bacteria can cause disease. This bacterium is gram negative non spore forming coccobacillus, endemic in north America and Eurasia. It is of two subtypes-Type A and Type B. The sick prairie dogs had type B F. tularensis.

3. Antibiotics used for treatment include streptomycin, gentamicin, doxycycline, and ciprofloxacin for 10-21 days. Streptomycin and gentamycin may be injected directly in muscle or veins. Treatment can be given if there is pneumonia or meningitidis.

4. Preventive control measures include no holding wild animals with bare hands and avoiding sick animals. Exposed skin should be covered properly with appropriate clothing. Insect repellants should be used in areas endemic. Ticks attached should be removed as soon as possible. Drinking water should be clean and boiled. Wild meat should not be eaten raw.

5. Ticks are arthropod vectors that spread F. tularensis. These include Amblyomma, Dermacentor, Haemaphysalis, and Ixodes. Others include mosquitoes, true horseflies and deerflies.