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

128 BACTERIOSESDenmark examined 1,458 pigs; serotype O:3 was isolated from the feces of 360(24.7%) animals. Fecal contamination of the carcass varied with the eviscerationtechnique. In the manual procedure, which is the traditional technique, frequencywas 26.3%, while in the mechanical procedure—suggested along with plugging theanus and rectum with a plastic bag—it fell by 1% to 2.2%, depending on the regionof the carcass (Andersen, 1988). The clinically important serotypes, O:3, O:5,27,and O:8, have been isolated from chopped pork, pig tongue, and from chicken.Swine slaughterhouse workers are an occupational group at risk of being infected.Enzyme-linked immunosorbent assay (ELISA) was used to examine serum samplesfrom 146 workers in Finland; antibodies were found for serotype O:3 in 19% ofthem and in 10% of blood donors used as controls. The tonsils of 31 of 120 pigsfrom the same slaughterhouse yielded positive cultures for serotype O:3 (Merilahti-Palo et al., 1991). In a similar study conducted in Norway, 25 (11.1%) of 316slaughterhouse workers and 9.9% of 171 veterinarians were positive for IgG antibodiesto serotype O:3. Counter to expectations, of 813 army recruits, prevalencewas higher among those from urban areas (15.2%) than from rural areas (Nesbakkenet al., 1991).Milk and water are vehicles of infection, among others. An outbreak in 1976 wasattributed to pasteurized chocolate milk. Another outbreak occurred in New York in1981, when 239 people became ill. The largest outbreak of all occurred in severalU.S. states and affected 1,000 people who drank recontaminated pasteurized milk.Unlike other outbreaks, the infection was caused by very rare serotypes (O:13a,O:13b). Pasteurization is effective in destroying the agent, and thus it is assumedthat contamination occurred afterward. Water contaminated by animal fecal matterhas been assumed to be the common source of infection in various Nordic countriesin Europe and in the US. A small familial outbreak occurred in Canada; it wascaused by serotype O:3, which is responsible for about 75% of all human cases inthat country. The agent was isolated from two family members and from water froma shallow well that may have been contaminated by dog feces swept in by heavyrains. The strains from the patients and the water had the same characteristics(Thompson and Gravel, 1986).It is often difficult to identify the source of infection. Foods may contain a smallnumber of pathogenic Y. enterocolitica within a large population of other bacteria,primarily environmental species of Yersinia spp. and nonpathogenic serotypes of Y.enterocolitica. Isolation and enrichment procedures are not always able to detect theetiologic agent (Schiemann, 1989).Blood transfusion is another route for human-to-human transmission. Althoughrare, the consequences of such cases are usually serious. From April 1987 toFebruary 1991, there were 10 cases in the US of bacteremia caused by transfusionof red blood cells. The final six of these patients showed fever and hypotensionwithin 50 minutes of transfusion. One patient suffered explosive diarrhea within 10minutes of transfusion. Four of the six died within a period of 12 hours to 37 days.The serotypes isolated were O:5,27 (4 cases), O:3 (one case), and O:20 (one case)(CDC, 1991). Blood donors were interviewed and some acknowledged having haddiarrhea in the 30 days prior to donating blood; one had diarrhea the same day andtwo indicated they had had no gastrointestinal complaints. In Great Britain, four ofa total of six cases were fatal in 1988. Two cases occurred in Scotland in four monthsalone and both people died (Prentice, 1992; Jones et al., 1993). Prentice (1992) esti-