The Possible Role of Rodent in Transmission of Salmonellosis To Man
By
Nashwa, O. Khalifa * and Ebtesam, M. Mazyed **
* Dept. of Zoonoses, Fac. Vet. Med. Benha Univ. and **Dept. Bacteriology, Serology, Animal Health Research Institute, Dokki, Giza, Egypt.
Summary
A total of 100 rodents were trapped alive from poultry farms, rabbit farms, sewers, shops and human houses from different localities in Kaliobia governorate. Trapped rodents were identified as Rattus rattus (40%) Rattus norvegicus (35%) and Mus musculus (25%). Intestinal contents of trapped rodents were screened bacteriologically to recover Salmonella spp. Salmonella spp. was isolated from 13 (13%) trapped rats and mice and the isolates were belonged to S. typhimurium and S. enteritidis serotypes. The identified Salmonella spp. were more prevalent in Rattus norvegicus than Rattus rattus and Mus musculus and in rodents trapped from poultry farms and sewers than the other localities. The presence of Salmonella spp. in trapped rats and mice inhabit animal farms and human houses, is an indication of contamination and neglected hygienic measures. The public health importance of salmonella and control measures were discussed.
Introduction
Rodents are common commensal pests of worldwide distribution. They cause considerable damage to stored production and building and transmitt diseases (Healing, 1991). Salmonellosis is the most wide spread zoonosis in the world. All Salmonella infection may be considered zoonoses except S. typhi and the paratyphoid serotypes A and C are species specific for man (Acha and Szyfres, 1989). Salmonella enterica serotype typhimurium was originally isolated from mice. (Santos et al. 2001) and isolated from both captive and wild rodents (Healing, 1991). Rats excrete Salmonella in its faeces ranging between 2 and 4 months following infection (Badi et al. 1992) and rat can voided up to 40 pellets per day (Meehan, 1984). Infected dropping not only represent a contamination risk to humans, either through direct contact with food stuffs or food contact surfaces, but may also act as a reservoir of Salmonella in the rat population, reinfecting other animals. Infected mouse implicated as a source of Salmonella in infected poultry house where droppings contained in some cases up to 104 organisms. (Davies and Wray, 1995). Salmonellosis is an important disease both for human health and for the economic losses that are caused in poultry industry (Hoop, 1997). S. enteritidis has become the most common serotype of Salmonella isolated from humans worldwide (Herikstad et al. 2002) and its clinical symptoms are included abdominal cramping, fever, vomiting and bloody diarrhea (Voetsch et al. 2004).
The goal of this study was to determine the prevalence of Salmonella spp. in rodents that inhabit animal farms and human dwellings aiming to asses the potential risk posed by these pests to the humans.
Materials and Methods
Collection and identification of rodents :
A total of 100 apparently healthy rats and mice were trapped alive by using ordinary wire spring cage live traps from different localities associated with humans and animals in Kaliobia governorate. Traps were baited with proteinous bait and placed in and around animal farms and human dwellings at a distance of 20 meters between each trap. Trapped rats and mice transferred to laboratory where they anaesthetized and identified according to Meehan (1984).
Sampling :
About 1gm of captured rodent intestinal content was added to 9 ml of non-selective preenrichment medium, buffered peptone water as described by Meerburg et al. (2006).
Isolation and identification of Salmonella spp.:
The prepared samples in buffered peptone water were incubated at 37°C for 24 hours. Aliquot of 1ml of pre-enrichment broth was inoculated into 10 ml of selenite-f broth (Oxoid) and then incubated overnight at 37°C. Aloopful of selective enrichment broth was surface plating on Salmonella and Shigella (S.S.) agar (Oxoid) and incubated for 24 hours at 37°C. Colonies (non-lactose fermenters) of typical growth were pale with or without black center were picked up and confirmed by biochemical tests according to Edwards and Ewing (1986) by sugar fermentation, H2S production, indole production, methyl red, Voges Proskauer, citrate utilization, nitrate reduction, catalase, urease and gelatin liquefaction.
Serotyping of isolates :
Suspected conlonies were serologically identified by using rapid diagnostic antisera against Salmonella typhimurium and Salmonella enteritidis (Welcome Diagnostic A Division, Dartfoed, England). The serotyping of salmonella was done according to Herikstad et al. (2002) suspected colonies were mixed with drop of antisera and left for 30 seconds. Positive result indicated by area of agglutination.
Results and Discussion
A total of 100 rodents were trapped alive from poultry farms, rabbit farms, sewers, shops and human houses from different localities in Kaliobia governorate, table (1). Trapped rodents were identified as Rattus rattus (40%), Rattus norvegicus (35%) and Mus muscles (25%). A result in accordance with previous study by (Nashwa- Khalifa, 1999).
Intestinal contents collected from anesthetized rats and mice were screened bacteriologically to recover Salmonella spp. Table (2) proved that Salmonella spp. were isolated from 13(13%) of rodents. Our results were lower than that reported in rats and mice by Akella and Samaha, (1986) (20%) in Edfina area, Alexandria, Egypt, while they were higher than those demonstrated in Rattus norvegius by Hilton et al., (2002) who found that the prevalence rate were 8% and 10% in faecal and rectal samples respectively in West Midland U.K. Battersby and Webster (2001) and Pocock et al. (2001) In U.K. failed to isolate Salmonella from house mice and concluded that rodents are probably not important primary sources of Salmonella infection in the United Kingdom, although they do seem to act as vectors in special cases where they have become infected by livestock.
Table (3) pointed out that Salmonella spp. isolated from rats and mice were belonged to S. typhimurium and S. enteritidis serotypes. A finding was similar to that identified by (Akella and Samaha, 1986). From the present results it is obvious that Salmonella serotypes were prevalent in Rattus norvegicus than Rattus rattus and Mus musculus. An observation supports those noticed by Hilton et al. (2002) and Meerburg et al. (2006) who recorded that Rattus norvegicus is a potential zoonoses transmitter of Salmonellosis. Also pet rodents purchased at retail pet stores incriminated as a potential source of human Salmonella infection in United States and England by Smith et al. (2005) and Swanson et al. (2006), respectively.
Table (4) declared that rodents trapped from poultry farms, rabbit farms, sewers, shops and human houses were positive to S. typhimurium and S. enteritidis and the highest prevalent rate were reported in rodents trapped from poultry farms and sewers. This may be due to greater concentration of rodents in poultry farms and sewers especially sewer, brown rat (Rattus norvegicus) which enhance the occurrence of Salmonella through contact with infected faecal shedding of animal and man and this may be explained the high percent obtained especially in Rattus norvegicus. A finding was similar to that reported by Gomez Villafane et al. (2004) and Meerburg et al. (2006). Infected poultry flocks are infecting the mice, which then serve as a reservoir for Salmonella re-infections. The prevalence tend to be lower in mice in units with no history of Salmonella in poultry (6% and 4%) compared with those with recent Salmonella infection 31.8% and 31.3%. Davis and Wray (1995) since house mice can act as reservoirs of infection and can re-infect poultry with Salmonella, their control needs to be considered where there are Salmonella prone livestock (Rose et al. 2000). Gomez Villafane et al. (2004) studied the prevalence of Salmonella spp. in Rattus norvegicus and Rattus rattus inhabit poultry farms and suggests that rats of poultry farms transmit S. enteritidis and indicates the application of prophylactic measures in poultry farms which must include control of wild rodents. (Huici et al. 1999) found a positive relationship between isolation of Salmonella from human and the consumption of chicken, eggs and their products and Salmonella infections constitute problem for broiler industry. Wild rodents may spread zoonotic bacteria between animal farms and this may be greater when contact with livestock is more likely and rodenticides are used less often (Leirs et al. 2004). Salmonella prevalence may increase when rodents are caught near a Salmonella spp. positive herd or flock (Meerburg et al. 2006). Meerburg et al. (2004) advised to apply effective rodent management that is in line with organic principles to protect livestock and human health.
In conclusion the present study proved that the Salmonella spp. could be recovered from trapped rats and mice inhabit animal farms and human houses. Therefore, it is necessary for concerned public health authority with veterinary service to impose specific control strategies against wild rodents.
Table (1): The localities from which different species of rodents were trapped.
Localities Rattus rattus Rattus norvegicus Mus musculus Total
No. % No. % No. % No. %
Poultry farms 8 32 9 36 8 32 25 25
Rabbit farms 9 40.9 6 27.2 7 31.8 22 22
Sewers 5 27.7 11 61.1 2 11.1 18 18
Shops 7 50 4 28.5 3 21.4 14 14
Human houses 11 52.3 5 23.8 5 23.8 21 21
Total 40 40 35 35 25 25 100 100
Table (2): Occurrence of Salmonella spp. isolated from rodents
Species of rodent Examined number Positive isolates
No. %
Rattus rattus 40 4 10
Rattus norvegicus 35 7 20
Mus musculus 25 2 8
Total 100 13 13
Table (3): Occurrence of Salmonella serotypes isolated from rodents
Salmonella serotypes Rattus rattus Rattus norvegicus Mus musculus Total
No. % No. % No. % No. %
S. typhimurium 2 25 4 50 2 25 8 61.5
S. enteritidis 2 40 3 60 0.0 0.0 5 38.5
Total 4 30.8 7 53.8 2 15.4 13 100
Table (4): The localities of rodent positive to Salmonella serotypes.
Localities Salmonella typhimurium Salmonella enteritidis Total
No. % No. % No. %
Poultry farms 3 75 1 25 4 30.7
Rabbit farms 1 100 0.0 0.0 1 7.7
Sewers 3 60 2 40 5 38.5
Shops 0.0 0.0 1 100 1 7.7
Human houses 1 50 1 50 2 15.4
Total 8 61.5 5 38.5 13 100
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الدور الممكن للفئران في نقل مرض السلامونيلوزيس للإنسان
* نشوه عثمان خليفة ،** وابتسام محمد مزيد
* قسم الأمراض المشتركة – كلية الطب البيطرى – جامعة بنها
** قسم البكتريولوجي والسيرولوجي – معهد بحوث صحة الحيوان بالدقى .
أجريت هذه الدراسة للكشف عن ميكروب السلامونيلا في الفئران والجرذان. وقد تم صيد عدد 100 من الفئران والجرذان من أماكن مختلفة متصلة بالإنسان والحيوان بمحافظة القليوبية وذلك باستخدام المصيدة علي شكل صندوق من السلك ولها قاعدة خشبية . وقد تم صيد الفئران من مزارع الدواجن ومزارع الأرانب والمجارى والمحلات التجارية ومن منازل الإنسان. وقد تم جمع محتوي الأمعاء للفئران بعد تخديرها وأجريت التجارب المعملية اللازمة لعزل الميكروب وتصنيفه وتم عزل السلامونيلا من 13 (13%) فأر وجرذ أسفرت النتائج الإيجابية للفحص السيتولوجي للعترات المعزولة عن تصنيف السلامونيلا إلي عترة السلامونيلا تيفي ميوريم والسلامونيلا انترتيدز وكانت نسبتها عالية في الفأر النرويجي بالمقارنة بكلا من الفأر والجرذ المنزلى وكذلك كانت نسبتها عالية في الفئران والجرذان التى تم صيدها من مزارع الدواجن والمجارى. ويعتبر وجود ميكروب السلامونيلا في كلا من الفئران والجرذان تحت الدراسة مؤشر للتلوث وسوء الإجراءات الصحية. وتم مناقشة الأهمية الصحية للميكروب والطرق المقترحة للمكافحة .
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