Management of Outbreak of Salmonellosis in a Pig Farm Revealed Human Source of Infection in Cameroon

Food-borne Zoonoses such as salmonellosis are major public health problem worldwide. In this study, we described the management of an outbreak of salmonellosis in a pig farm in the South region of Cameroon. Laboratory investigation based on PCR, isolation & identification and antibiogram tests indicated that the Salmonella strain was sensitive to gentamycin and neomycin, but resistant to tetracycline and penicillin. Neomycin was administered to the pigs while gentamycin was used to treat the farmer itself. From our findings and investigations, the source of infection could be from the man in charge of feeding those animals. This calls for a strong collaboration among One Health sectors for a management of zoonotic diseases.


Introduction
Salmonellosis is a zoonotic food-borne bacterial disease caused by Salmonella sp. Over 2,500 serotypes (serovars) of Salmonella are known to date [1]. The bacteria are generally transmitted between humans and animals through contact, or consumption of contaminated food of animal origin, mainly eggs, milk, meat and chicken.
Clinical manifestations of Salmonellosis include fever, diarrhea, and abdominal pains within the first 3 days of infection. Some cases may be self-limited while others may require medical care and hospitalization. According to Centers for Disease Control and Prevention (CDC) report, Salmonella causes about 1.2 million illnesses,

23,000 hospitalizations, and 450 deaths in the United States every
year. Food is the source for about 1 million of these illnesses [2].
Moreover, the economic costs associated with Salmonella illnesses are staggering, ranging from $4 billion to $11 billion dollars annually [3]. Antibiotic are used for treatment. However, resistant strains of this bacterium are a handicap to antibio-therapy. Salmonella infections is a worldwide disease present in every country with high prevalence in areas of intensive animal husbandry, especially poultry, cattle, and pig farming [4]. In this study, we are reporting a case of salmonellosis detected in a pig farm where the herd man was the source of contamination. Antibiotic treatment on both animals and human was based on sensitivity tests.

Materials and Methods
A total of 30 samples comprising of 15 anal swaps and 15 blood samples from clinically sick 10 piglets and 5 adults pigs were collected and transported to LANAVET Annex Yaoundé for analysis.
Blood and swap samples were first subjected to PCR. After the PCR results, bacteriological analysis of swap samples using isolation and identification were followed by antibiogram.

Molecular Detection of Salmonella sp.
We extracted DNA from blood and swap samples using Qiagen

Isolation and Identification of Salmonella sp.
We cultured, isolated and identified Salmonella as described by Nair et al. [6] with slight modification. Briefly, sample from the transport swab was pre-enriched in peptone water at 37°C for 18 h and then cultured on Rappaport-Vassiliadis broth and Xylose Lysine Desoxycholate (XLD) agar. Characteristic colonies were subjected to passages on the same media before selection for biochemical test using API-20E kit according to the manufacturer's protocol.
The plate was incubated for 24h at 37°C. We used inhibition size of each disk to characterize sensitive and resistant drugs.

Results and Discussions
Both PCR assay and isolation and identification detected Salmonella sp in the samples. All the swap and only two blood samples were positive with PCR, showing approximately 284 bp fragments. Furthermore, Api-20E findings were also identical to Salmonella with 99% confidence. In addition, the antibiogram test indicated that the strain was sensitive for Gentamycin (2.2cm) and Neomycin (2.3cm), but resistant to penicillin and tetracycline.
This confirmed the abusive use of antibiotics in animal farming.
Among the most used drugs in veterinary medicine, penicillin and tetracycline long acting are on the first line.