We detected high prevalence of Salmonella enterica ssp. enterica in the feces of the production animals slaughtered for human consumption in Burkina Faso. Salmonella was especially common in the poultry (55%) and cattle (52%) feces samples. The levels of Salmonella in poultry can vary depending on the country, the nature of the production system and the specific control measures in place. In some EU countries chicken flocks are virtually free from Salmonella whereas in the US a contamination rate up to 60% was detected . In Japan, Salmonella was isolated from 36% of the broiler fecal samples . In Gambia, the detected rate of Salmonella in chicken feces was higher, 67% , than what we detected from the chicken feces. In comparison, only 11% of chicken reared at intensive poultry farms in Nigeria were found to be infected .
The levels of Salmonella rates reported in beef are usually lower than in chicken. Salmonella carriage was reported to be 1.4% in cattle in Great Britain  and 0.5% in Japan . In Ethiopia, 4% of the feces of slaughtered cattle were contaminated by Salmonella. The high rate of Salmonella detected in our study might be explained partly by the method used for strain isolation and partly by the animal husbandry practices. In Burkina Faso, cows and sheep mostly roam freely at pasture in the bush. The wild animals, such as hedgehogs, living in such places can contaminate grass with their excreta, which, as shown in our study, can have high carriage rate of Salmonella. We found 16% of the swine feces samples to be contaminated by Salmonella. Salmonella contamination rates for pigs reported in literature vary from 9% to 23% in Europe [18, 22, 24], to 3% of porcine fecal samples in Japan  and 8% in Kenya . In accordance to the high rates of Salmonella detected in the feces samples, our previous studies on the prevalence of Salmonella in retail meats and beef intestines in Burkina Faso also revealed high numbers of Salmonella, especially in chicken (37-57%) [13, 14].
Several of the serotypes isolated in this study, including S. Typhimurium, S. Muenster, S. Derby, S. Virchow, S. Hato, S. Bredeney, S. Stanley and S. Anatum, have frequently been implicated in outbreaks or sporadic cases of human illness . In Africa, as elsewhere in the world, S. Enteritidis and S. Typhimurium are the most common causes of human salmonellosis . Interestingly, S. Enteritidis was not recovered from the animal feces in our study and not from the human isolates in Burkina Faso either . The main serotypes found in both animal and human feces samples from Burkina Faso included S. Typhimurium (from poultry) and S. Muenster (from all the studied animal species). S. Derby was the most common serotype we detected in the chicken feces, as it was in the chicken carcasses [13, 14]. World-wide, a wide range of Salmonella serotypes have the ability to colonize poultry: S. Typhimurium, S. Enteritidis, S. Hadar, S. Virchow, S. Infantis and, recently, S. Paratyphi B var. Java have all been frequently isolated from poultry in several countries , none of which were among the most common serotypes in poultry in Burkina Faso. Elsewhere in Africa, S. Enteritidis was the most common serotype detected in chicken feces in Zimbabwe  and S. Typhimurium in Algeria . Notably, we isolated one S. Typhi strain from the chicken feces, as we did previously from a chicken carcass .
The S. Typhimurium isolates from chicken feces in Burkina Faso were multi-resistant to the commonly available antimicrobials ampicillin, chloramphenicol, streptomycin, sulfonamides and trimethoprim. This is a typical pattern found in the Salmonella strains with a sub-Saharan distinct genotype causing epidemic invasive disease . Bacteremia caused by multi-resistant S. Typhimurium strains is a serious public health problem in Africa and they are significantly associated with increased mortality . Such S. Typhimurium isolates have been reported from e.g. Zaire , Kenya , Malawi  and Central Africa . Although antimicrobial use for animals is under veterinary prescription control in Burkina Faso, farmers still use unprescribed antimicrobials as growth promoters or treatment for cattle, poultry and swine. This practice leads into a possibility that bacterial resistance developing in the food animals transfers to the human population thus posing a risk for public health by spreading of the resistance . It would be essential to study the genotype of our S. Typhimurium isolates from poultry further in order to know if the invasive genotype also occurs in animals as the environmental reservoirs and host ranges of invasive salmonella strains in Africa are still unknown . Our S. Typhimurium isolates from chicken and humans had the same phage type DT 56. This phage type was in Kenya among the most common phage type from adult patients . In developed countries, a phage type DT 104 has often been associated with outbreaks of multiresistant S. Typhimurium infection in both man and animals . Only two isolates in our study was resistant to the newer antimicrobials; S. Muenster from the poultry feces was resistant to nalidixic acid, as was S. Urbana from the cattle feces, furthermore, its sensitivity to ciprofloxacin and cefotaxime was decreased.
PFGE provides valuable phylogenetic-relationship inference for Salmonella at serotype and strain level [38, 39]. Our cluster analysis revealed close genetic relationship between some human and animal strains belonging to the same serotypes. Notable similarity of the chicken and human isolates indicates that chicken may be a major source of Salmonella transmission to humans. Also in Senegal, a study detected a high degree of similarity among S. Hadar, S. Brancaster and S. Enteritidis from poultry meat and humans by using PFGE . Besides through food, direct transmission from chicken to humans could easily happen in Burkina Faso, since chickens roam free scattering their feces anywhere in the house yards. Although, in these surroundings it is also possible that it is rather chicken which get transiently infected with the typical human Salmonella strains. However, the study conducted recently on isolates from infected children and their households in the Gambia did not support the hypothesis that humans and animals living in close contact in the same household carry genotypically similar Salmonella serotypes .
We found out that the prevalence of Salmonella in hedgehog feces was particularly high (96%). In Burkina Faso, hedgehogs live in a variety of habitats where they dig their burrows, spend most of the daylight hours asleep, and emerge at night to forage. Hedgehogs can serve as reservoirs of Salmonella in many ways. During the night, villagers go to catch them as a meat source for the next day. During the rainy season, feces of animals including hedgehogs pollute the water sources such as rivers and wells. At the countryside many people are dependent on these sources for their potable water. In developed countries, people having exotic hedgehogs as pets have fallen sick with salmonellosis . In these cases, the commonly detected Salmonella serotype has been S. Tilene . Since we found several S. Tilene strains in our cattle and chicken meat samples during our previous study , we wanted to investigate a possible link between the Salmonella carriage of the production animals and hedgehogs, which share the same pastures for foraging. Indeed, we found hedgehogs in Burkina Faso to carry many Salmonella serotypes common also in the production animals, but no S. Tilene was detected, not in feces of the studied hedgehogs or of the other animals.
S. Muenster isolates were obtained from the feces of all the studied animal species and humans and their genetic relatedness in PFGE analysis was 90 to 95%. Thus, it is possible that the same strains of S. Muenster are able to infect many different hosts. Hedgehog feces might infect both cattle and swine foraging freely, since Salmonella can persist in the environment for several months to more than a year [41, 42]. The production animals and the hedgehogs might all be able to transfer Salmonella further to the humans. We have previously shown the production animals to be potential carriers of virulent Escherichia coli to humans as well . There is no previous information on the frequency of wild animals carrying enteropathogenic bacteria in Burkina Faso, apart from the Salmonella carriage of hedgehogs reported here.