Some E. coli pathogenic strains may cause enteric or extra-intestinal disease. In dogs and cats, strains of extra-intestinal pathogenic E. coli (Ex-PEC) produce alpha-hemolysin and cytotoxin necrotizing factors (CNF). In this study the results of a high neonatal mortality in puppies associated with hemolytic CNF positive E. coli are reported.
A 10-day-old litter of 5 puppies showed weakness and diarrhea and, 2 days later, 4 of them died. At the same time, the bitch showed hyperthermia and was treated with amoxicillin. One puppy survived through artificial feeding and recovered in few days without antibiotic treatment.
Necropsy was conducted on one puppy and microbiological and histopathological exams were performed on lung and kidney. Moreover, the bitch's milk was analyzed for standard microbiological exams. E. coli isolates were tested for CNF. Two weeks later, fecal samples from the bitch and the survived puppy were collected for a control microbiological analysis.
At necropsy severe lobar pneumonia with dark red mottled consolidation and bilateral marked nephrosis with parenchymal softening and congestion were observed.
Histopathology of the lung revealed severe fibrinous bronchiolar-alveolitis associated with rod-shaped bacterial aggregates and diffuse interstitial lymphocytic infiltration; the kidney showed severe multifocal necrosis of the tubular epithelium and diffuse severe congestion of the parenchyma.
Hemolytic CNF positive E. coli was isolated from milk, lung and kidney.
Low bacterial load of hemolytic CNF positive E. coli was isolated from the mother's faeces two weeks after the outbreak, while the hemolytic E. coli isolated from the puppy's sample was CNF negative.
It is hypothesized that the bitch's milk could be the main source of Ex-PEC infection causing high puppies mortality. The role of "healthy carrier" of the bitch could not be excluded: stressful conditions, such as pregnancy and delivery, would change the host-pathogen dynamics possibly increasing the release of the infectious burden.