Intestinal myoelectric activity in parasitized dogs

Abstract
Dogs were studied during the enteric phase of infection with the nematode Trichinella spiralis to determine whether symptoms referrable to the gastrointestinal (GI) tract and the rejection of the parasite from the intestine are accompanied by alterations in normal patterns of intestinal motility. Motility was measured in unanesthetized dogs during primary and secondary infections by monitoring electrical activity of intestinal smooth muscle with electrodes permanently implanted on the serosal surface. Dogs were examined daily after they ingested 1, 2 or 3 .times. 104 larvae/kg body wt. Some dogs were examined after receiving these doses and, 6 wk later, a challenge dose of 2 .times. 104 larvae/kg body wt. The overall host response to infection was followed by observing the development of anorexia, diarrhea and weight loss, by determining circulating eosinophil levels and specific antibody titers and by recovering 2nd-generation larvae from skeletal muscles 30 days postinfection. Changes in normal motility patterns occurred as early as 18 h after primary infection but were most marked 3-4 days postinfection when the hosts were diarrheic and refused food. By 6 days postinfection, diarrhea subsided and the dog began to eat readily. Motility returned to normal 11-15 days postinfection. Secondary infection failed to produce any significant deviation from the control pattern of motility and did not elicit any outward signs of disease. The absence of noticeable evidence of infection following challenge was attributed to acquired resistance induced by primary trichinosis. This resistance was reflected by the appearance of significant numbers of infective larvae in the feces after secondary infection and the lack of a significant rise in the number of larvae that were encysted in muscle, as compared with a primary infection. Changes in intestinal motility may be associated temporally with symptoms related to the GI tract and the magnitude of change is probably inversely related to the resistant state of the host.