zoonoses and communicable diseases common to ... - PAHO/WHO

140 BACTERIOSESThe disease is usually mild and lasts from one to seven days, but there have beenfatal cases (Klontz, 1990). Some extraintestinal cases have occurred, such as infectionof wounds, ears, and eyes, and there have also been isolates from blood. In someof these latter cases, there is doubt as to whether they were caused by V. parahaemolyticusor other halogenous Vibrios. Sautter et al. (1988) described the case ofa foot wound infected by Kanagawa-negative V. parahaemolyticus. A hospitalemployee suffered a superficial abrasion and a small bruise on the ankle and traveledthe following day to the eastern coast of the US. The abrasion began to ulcerate,edema and erythema formed around the ulcer, and the area became painful. By thesixth day, the erythema had grown to 18 cm and a 4 cm ulcer appeared. The patientwas treated with dicloxacillin for 14 days. After two days of treatment, the ulcerbegan to leak a serosanguineous fluid, from which V. parahaemolyticus was isolated.Treatment was completed, the patient recovered, and the cultures were negative.Generally no treatment other than rehydration is required for food poisoningcaused by V. parahaemolyticus. The use of antibiotics should be reserved for prolongedor severe cases.The Disease in Animals: V. parahaemolyticus causes only an inapparent contaminationor infection in fish, mollusks, and crustaceans.Source and Mode of Transmission: The major reservoir is seawater. Fish, mollusks,and crustaceans acquire the infection from seawater. When humans eat themraw or insufficiently cooked, they act as a source of infection. Humans need a loadof 10 5 –10 7 of V. parahaemolyticus to become infected (Twedt, 1989).Recently caught fish have a V. parahaemolyticus load of only 1,000 per gram orless and recently harvested mollusks have a load of some 1,100 per gram; i.e., a loadlower than that needed to infect humans (Twedt, 1989). It is thus assumed that thehigher load is caused by handling of these seafoods, permitting multiplication of V.parahaemolyticus in the food. V. parahaemolyticus reproduces in a very short time(approximately 12 minutes) and exposure of the food to room temperature for a fewhours is enough to allow the bacterial load to produce poisoning in man.A very important factor in the epidemiology of the disease in many countries isthe custom of eating raw seafood. Japan is one of the countries with the most outbreaksof food poisoning caused by V. parahaemolyticus because raw fish, shellfish,and crustaceans are consumed there. In the US, the most common source of poisoningis the consumption of raw oysters and even some uncooked or undercookedcrustaceans.Carrier status lasts for a few days and there are no known cases of secondaryinfection.Role of Animals: The role is indirect and transmission is through food. The onlyvertebrates involved in the chain of transmission to man are fish, along with mollusksand crustaceans.Diagnosis: A diarrheal disease occurring during the warm months and in associationwith the ingestion of seafood should lead one to suspect the possibility of foodpoisoning caused by V. parahaemolyticus. Certain diagnosis is obtained throughisolation and characterization of the etiologic agent.The medium most often used for culturing feces is thiosulfate citrate bile saltssucrose (TCBS) agar. The colonies in this medium take on a green or bluish color,