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Herd problems and occupational zoonoses of Salmonella enterica serovars Typhimurium and Enteritidis infection in diarrheic cattle and buffalo calves in Egypt

Introduction Salmonella infections in dairy calves have many impacts on animal and human health that are considered major worldwide problem. Substantial economic losses were manifested through mortality and poor growth of infected animals as well as the potential of zoonotic transmission (Smith et al 2004). Many outbreaks with high prevalence of clinical and subclinical Salmonella infections have been reported in cattle and calves worldwide, which encountered many isolated serovars that considered host-adapted Salmonella for cattle (Lance et al 1992; Radke et al 2002; Veling et al 2002; Berge et al 2008; Daly & Neiger 2008). Herikstad et al (2002) reported that Salmonella enterica serovar Typhimurium (ST) is the most frequently isolated from foodborne outbreaks throughout the world. Salmonella enterica serovar Enteritidis (SE) also is a major cause of foodborne diseases (Rodrigue et al 1990). In Egypt, a varying prevalence of Salmonella infections in calves was recorded with predominance of ST and SE serovars (Seleim et al 2004; Younis et al 2009; Moussa et al 2010, 2012). It was reported that over 90% of the farms had at least one Salmonella-positive culture (Fossler et al 2004). Considering these high herd-level prevalence values, it would seem logical that fecal shedders within a herd represent a potential point of intervention to mitigate public health risk. In particular, those occupationally work or otherwise interact with livestock are also at risk of zoonotic infection (Vanselow et al 2007). In addition, indirect transmission can be caused by either contamination of crops as well as water by manure contamination used as a fertilizer or during manure run-off (Islam et al 2004). Food chain contamination during slaughtering animals and contamination in animal markets are additional sources of transmission (Mead et al 1999). All these potentials of zoonotic infections are possible to occur in Egypt. However, there is lack of reported enteric non-typhoid Salmonella human infection. Antimicrobial resistant strains of Salmonella pose a severe and costly animal health problem, by prolonging illness and decreasing productivity through higher morbidity and mortality rates. Moreover, it impaires treatment of human in case of zoonotic infections. Strains of Salmonella isolated from animals and human that are resistant to antimicrobial agents have been reported. (Angulo & Griffin 2000; Breuil et al 2000, Koirala, 2011; Sugawara et al 2012). In Egypt, multidrug resistant isolates of ST and SE from diarrheic calves was detected and Abstract. This study aimed to investigate Salmonella enterica serovar Typhimurium (ST) and Salmonella enterica serovar Enteritidis (SE) infections of diarrheic calves in bovine dairy herds and their farm workers. Antimicrobial drug resistance profile of the isolates was determined by standard disc diffusion assay. Fecal swabs were collected from diarrheic calves aged from one week to three months (Median age 33.5 days); from three farms representing cattle, native breed buffalo and cross-breed buffalo farms. Each farm was visited every three months for one year, from March 2011 to February 2012. Collected Swabs were examined by conventional bacterial culture and serotyped by multiplex PCR. Results showed that Salmonella was isolated from 42/255 (18.66%) diarrheic calves and 27/35 (77.14%) calves died from diarrhea. Incidence of ST was significantly higher in calves died from diarrhea than diarrheic calves (P>0.001). On farm level, isolation rate of Salmonella was significantly higher in dead calves in cross-breed buffalo farm than native breed buffalo and cattle farms (P>0.001). On other hand, the incidence of Salmonella among stool swabs of farm workers caring the calves was 8.13%; with isolation rate of (2.32%) ST, (1.16%) SE and (4.65%) other Salmonella serovas. Isolates showed a high percentage of multi-drug resistant profile (63.88%). All isolates were completely resistant to oxytetracycline, danofloxacin and oxacillin. Enrofloxacin was the drug of choice. In conclusion, a high incidence of mutli-drug resistant Salmonella infections was detected in cattle and buffalo calves that might be associated with high mortality rate in calves and zoonotic potential to the farm workers. Adequate hygienic measures, proper immunization programs and regular training to the labor should be applied.