Mycobacterium avium Subsp. avium and Salmonella enterica Serotype Typhimurium Var. Copenhagen Phage Type DT2 in Pigeons

Introduction

P igeon breeding has a long-lasting tradition in the Czech Republic, and pigeon squabs are consumed by humans. Mycobacterium avium subsp. avium is one of causative agents of avian mycobacteriosis in birds, as well as in other animals and humans (Biet et al., 2005). Its occurrence in domestic pigeons has been described sporadically (Morita et al., 1994; Bougiouklis et al., 2005). Salmonella enterica serotype Typhimurium poses a real health risk for humans as the cause of food poisonings, and the occurrence of antimicrobial multiresistant strains is of great public health importance (Nielsen et al., 2009). Both pathogens can cause foodborne diseases in immunocompetent and immunesuppressed patients (Ullrich et al., 1992; Rabsch et al., 2002).

An outbreak of M. a. avium infection was confirmed in three pigeons from a flock in a small fancy breeding aviary in the southern Moravia region, Czech Republic (Kriz et al., 2010). The flock numbered 435 pigeons, which were kept in five lofts in poor hygienic conditions with contact to free-ranging birds. They were fed with commercial groats, which were stored under bad conditions, and a contact with small rodents, that is, mice, occurred. Clinical symptoms of diarrhea, loss of body condition, inability to fly, and ruffled feather had occurred in pigeons during few months before M. a. avium outbreak was diagnosed, and a veterinary practitioner suspected Salmonella spp. to be the cause at that time. The aims of our study were (1) to investigate if there was a coinfection by both pathogens and to (2) investigate Salmonella spp. isolates for antimicrobial sensitivity.

Materials and Methods

The whole flock of 435 pigeons was euthanized using carbon monoxide according to the law of the Czech Republic (Act No. 166/1999 Coll., on veterinary care and on a change of some related laws). Nodular granulomatous lesions were found in internal organs of 42 birds. Thirty three (78.6%) birds with nodular lesions were randomly selected for the study. Samples of liver and caecum were taken from each one pigeon. Liver samples were cultured for mycobacteria as described elsewhere (Matlova et al., 2005). The presence and numbers of M. a. avium in liver tissues were determined using the triplex quantitative real-time PCR (triplex qPCR) method described previously (Slana et al., 2010). Liver and caecum specimens were cultured using the ISO 6579:2002 method for Salmonella isolation (International Organization for Standardization, 2002; available at www.iso.org/iso/catalogue_detail.htm?csnumber=29315). The isolates were serotyped with agglutination O and H antisera and classified according to the Kauffmann-White scheme. The Salmonella Typhimurium isolates were phagotyped according to HPA London, United Kingdom, and examined by the disc diffusion method Clinical and Laboratory Standards Institute (CLSI document M31-A3; available at www.clsi.org/source/orders/free/m31-a3.pdf) for antimicrobial resistance to ampicillin (10 μg), amoxicillin/clavulanic acid (30 μg), apramycin (15 μg), colistin (10 μg), cefotaxime (30 μg), chloramphenicol (30 μg), enrofloxacin (5 μg), gentamicin (10 μg), kanamycin (30 μg), nalidixic acid (30 μg), neomycin (30 μg), streptomycin (10 μg), sulphamethoxazole/trimethoprim (25 μg), sulfisoxazole (300 μg), and tetracycline (30 μg).

Results and Discussion

M. a. avium was detected in a total of 31 (93.9%) pigeons. In 11 (33.3%) pigeons, Salmonella Typhimurium was isolated. Coinfection with both pathogens was found in 10 (30.3%). The infection with Salmonella Typhimurium was found alone in 1 (3.0%), and infection with M. a. avium alone in 21 (63.7%) pigeons. Neither pathogen was detected in one pigeon. The numbers of M. a. avium cells determined by triplex qPCR ranged from 10⁰ to 10⁹, corresponding most probably to different immune status of individual birds (Table 1).

All Salmonella spp. isolates were identified as Salmonella enterica serotype Typhimurium variant Copenhagen phage type DT2, and all were susceptible to all 15 antimicrobials tested. The variant Copenhagen is highly host-adapted to pigeons, and the phage type DT2 is the most commonly found among Salmonella Typhimurium strains isolated from pigeons, but its virulence for humans is low (Rabsch et al., 2002). Phenotype multiresistance patterns, for example, ACSSuT, were already found in pigeon Salmonella Typhimurium var. Copenhagen phage type DT2 strains (Frech et al., 2003). However, we did not find any such strains in our case.

There was no difference in clinical symptoms exhibited by pigeons infected by M. a. avium and/or Salmonella Typhimurium; pigeons had ruffled feather and were emaciated with occasional diarrhea. Coinfection of pigeons by both these pathogens has not been described. Natural M. a. avium infection with above-observed clinical symptoms in pigeons was described by Bougiouklis et al. (2005).

Two people (breeder and his sister) came into close contact with infected pigeons and occasionally ate pigeon squabs. They never had salmonellosis. However, they were not examined for Salmonella spp. by culture. Both people were tested for M. a. avium infection using tuberculin skin test, triplex qPCR examination of their sputa and feces, and chest X-ray and abdominal ultrasonography, all with negative results. Surveillance in eastern Germany carried out between 1974 and 1996 showed that Salmonella Typhimurium var. Copenhagen phage type DT2 was often isolated from pigeons and sporadically from infected humans (Rabsch et al., 2002).

As we also have found M. a. avium infection in 2 (10%) of squabs from the flock (unpublished data), the consumption of undercooked infected squabs might pose a health risk for humans, mainly for those immunocompromised (Adejumo et al., 2009).