Retrospective study on necrotizing enteritis in piglets in Switzerland

The re-emergence of necrotizing enteritis (NE) in Swiss pig breeding farms raised concern that, besides C. perfringens type C strains, additional C. perfringens toxinotypes might cause this disease. Therefore we retrospectively investigated the association of NE with C. perfringens type C or different C. perfringens toxinotypes. We evaluated pathological lesions, routine diagnostic bacteriology results, and multiplex real-time PCR analyses from DNA extracts of archived intestinal samples of 199 piglets from our diagnostic case load. 96.5% of NE cases and 100% of herds affected by NE were positive for C. perfringens type C genotypes. Animals without necrotizing enteritis revealed a significantly lower detection rate of type C genotypes. Non affected piglets showed a high prevalence for beta-2-toxin positive C. perfringens type A strains. Collectively, our data indicate that outbreaks of NE in piglets in Switzerland cannot be attributed to newly emerging pathogenic toxinotypes, but are due to a spread of pathogenic C. perfringens type C strains.

Phenotypic and genetic characterization of Pasteurella multocida and related isolates from rabbits in Switzerland

Several bacteria belonging to the family Pasteurellaceae are potential pathogens in rabbits. In particular, Pasteurella multocida is considered to be important, and outbreaks caused by this species result in considerable economic losses in rabbitries. However, Pasteurellaceae spp. isolated from rabbits are poorly characterized, and thus, proper identification of P. multocida isolates from these animals is problematic and often unsatisfactory, thereby hampering epidemiological investigations. Therefore, 228 isolates from rabbit populations originating from a breeding and fattening organization with group management and postmortem cases with pasteurellosis from individual owners were phenotypically and genotypically analyzed using biochemical tests and repetitive extragenic palindromic polymerase chain reaction (REP-PCR). Furthermore, 41 samples representing observed phenotypes were selected for phylogenetic analysis using 16S ribosomal RNA and rpoB genes. The REP-PCR typing and phylogenetic analyses correlated well and appeared to be distinct molecular methods for characterization of rabbit isolates. Phenotyping, however, diverged from molecular recognition, reflecting the problematic conventional diagnosis of these strains. The fermentation of sorbitol appeared to be an imprecise indicator for P. multocida subspecies classification. According to REP-PCR and sequencing results, 82% of the isolates were characterized as P. multocida subsp. multocida, 3% as P. multocida subsp. septica, and 5% as P. multocida. Further, 5% were identified as Pasteurella canis. The other 5% represented a homogeneous group of unknown species belonging to the Pasteurellaceae. Samples obtained from individual postmortem cases demonstrated a higher phenotypic and genetic heterogeneity than samples from group management rabbits.

Antibiotic resistance and genetic diversity in Staphylococcus aureus from slaughter pigs in Switzerland

Nasal carriage of Staphylococcus aureus was evaluated in pigs at slaughterhouse. The nasal cavities of 304 pigs from 54 herds were screened. Eighty-nine percent of the farms harbored pigs that were colonized with S. aureus. Among them, no MRSA were found, indicating a low prevalence. However, pigs were found to harbor S. aureus, which displayed resistance to penicillin (blaZ) (62.5%), tetracycline [tet(M)] (33.3%), streptomycin (strpS194) (27%), clindamycin [erm(B)] (4.1%), erythromycin [erm(B)] (4.1%), kanamycin (4.1%), chloramphenicol (catpC194) (2%) and gentamicin [aac(6')-Ie-aph(2')-Ia] (2%). The S. aureus isolates mainly belong to Ridom spa type t034 (31.3%), t208 (14.6%) and t899 (12.5%). These pig-associated spa types have not yet been detected in hospitalized human patients in Switzerland. Surveillance programs are now necessary at both inland and import levels to rapidly detect and suppress the emergence of MRSA in pigs in Switzerland.

Babesia capreoli infections in alpine chamois (Rupicapra r. Rupicapra), roe deer (Capreolus c. Capreolus) and red deer (Cervus elaphus) from Switzerland

Five cases of fatal babesiosis in free-ranging chamois (Rupicapra r. rupicapra) attributed to infections with Babesia capreoli were recently recorded in two regions of the Swiss Alps. To investigate the ecologic factors that possibly lead to those fatal B. capreoli infections in chamois, blood, ticks, and demographic data of 46 roe deer (Capreolus c. capreolus), 48 chamois, and nine red deer (Cervus elaphus) were collected in 2006 and 2007 in both affected regions. Whereas no parasitic inclusions were found by microscopical examination of blood smears, B. capreoli was identified by polymerase chain reaction/sequencing in blood of 12 roe deer (26%, 95% confidence interval [CI]: 14.3-41.1), one chamois (2%, CI: 0-6.1), and one red deer (11%, CI: 0.3-48.2). Prevalence of B. capreoli was significantly higher in roe deer compared with chamois (P<0.001). All 214 ticks were identified as Ixodes ricinus, and significantly more roe deer (63%, CI: 47.5-76.8) were infested compared with chamois (21%, CI: 10.5-35.0, P<0.001). Overall, prevalences of both tick infestation and Babesia infection increased significantly (P<0.001) with decreasing altitude, and Babesia-positive samples were detected significantly more often from animals with tick infestation compared with animals without ticks (P = 0.040). Our results indicate that roe deer may play an important reservoir role for B. capreoli. It is hypothesized that the expansion of the presumed vector I. ricinus to higher elevations and its increased abundance in overlapping habitats of roe deer and chamois may favor the spillover of B. capreoli from roe deer to chamois.

[Serological and clinical proof of freedom from Equine Infectious Anemia (EIA) in imported and domestic horses in Switzerland]

Since 1991, no cases of Equine Infectious Anemia (EIA) have been reported in Switzerland. Risk factors for introduction of the virus into Switzerland are still present or have even increased as frequent inapparent infections, large numbers of imported horses, (since 2003) absence of compulsory testing prior to importation, EIA cases in surrounding Europe, possible illegal importation of horses, frequent short-term stays, poor knowledge of the disease among horse owners and even veterinarians. The aim of this study was to provide evidence of freedom from EIA in imported and domestic horses in Switzerland. The serum samples from 434 horses imported since 2003 as well as from 232 domestic horses fifteen years of age or older (since older horses have naturally had a longer time of being exposed to the risk of infection) were analysed using a commercially available ELISA test. All samples were seronegative, indicating that the maximum possible prevalence that could have been missed with this sample was 0.5% (95% confidence).

Prevalence study of Staphylococcus aureus in quarter milk samples of dairy cows in the Canton of Bern, Switzerland

In the present study, the prevalence of S. aureus in mammary gland quarters of dairy cows in Switzerland was estimated and a risk factor analysis was carried out. Dairy cows were selected by one-step-cluster sampling with stratification by herd size. Forty-seven of 50 randomly chosen farms participated in the study, resulting in 603 cows and 2388 quarter samples. Milk samples were collected in all herds on two occasions two weeks apart. In 6% of cows (95% CI: 2.7-9.3%) at least one milk sample was positive for S. aureus and from 2% (0.8-3.2%) of all quarters, S. aureus was cultured at least once. In four quarters a latent S. aureus infection (agent detected and somatic cell count (SCC) <100,000cell/ml) was diagnosed. Multivariable hierarchic logistical regression analysis yielded five significant risk factors for observing S. aureus in a milk sample: high SCC, a S. aureus-positive neighbouring quarter, a palpable induration in the quarter, and a wound, scar tissue or crush injury affecting the teat. The type of housing (P=0.1596) was also a factor that remained in the model. The mentioned risk factors must be considered during the evaluation of herds with S. aureus problems. The occurrence of latent S. aureus infections emphasises that not only quarters with a high SCC but all quarters of all cows must be cultured for control measures to be effective.

Seroprevalence and characterization of pestivirus infections in small ruminants and new world camelids in Switzerland

The seroprevalence of pestivirus infections in small ruminants and new world camelids in Switzerland was determined. In 5'059 sera of sheep from 382 herds, 503 sera of goats from 54 herds and 109 sera of alpacas and lamas from 53 herds, population prevalences of 16.1% (sheep), 25.4% (goats) and 4.6% (new world camelids), respectively, were found. In order to determine the source of infection, the serological reactions were further characterized by cross-neutralization against two pestiviruses representing the genotypes BVDV (Bovine Virus Diarrhea Virus)-1 and BDV (Border Disease Virus)-1. Based on the ratio of respective antibody titres, 56.1% of the infections in sheep were induced by a BDV-1, 12.9% by a BVDV-1 and 31.0% by an unresolved pestivirus. In goats, the corresponding proportions were 23.4%, 10.2% and 66.4%, respectively. In Alpacas and Lamas, the source of infection of 1 animal was BDV-1 and that of 4 seropositive animals remained unresolved. In view of the phylogenetic relationship between pestiviruses, the unresolved source of infection is most probably attributable to other pestivirus genotypes circulating in small ruminants and new world camelids. Due to the predominance of pestiviral genotypes other than BVDV-1, the risk of transmission of BVDV from persistently infected small ruminants and new world camelids to cattle appears to be moderate, apart from close direct contact in mixed animal husbandry, communal pasturing and grazing in the Alps.

Intestinal Tritrichomonas foetus infection in cats in Switzerland detected by in vitro cultivation and PCR

Tritrichomonas foetus, a parasite well known for its significance as venereally transmitted pathogen in cattle, has recently been identified as a cause of chronic large-bowel diarrhea in domestic cats in the US, UK, and, more recently, also in Norway. In a period of 3 months (October to December 2007), 45 cats of Switzerland suffering from chronic diarrhea were investigated for intestinal infections, including a search for trichomonads. A commercially available in vitro culture system was used to screen for infection, complemented with a PCR and subsequent amplicon sequencing to support speciation. The PCR is based upon amplification of a sequence derived from the internal transcribed spacer region 1 (ITS1) on the ribosomal RNA gene (rRNA) using primers designed to detect a broad range of genera and species belonging to the family of Trichomonadidae. The method was furthermore adapted to the uracil DNA glycosylase (UDG) system in order to prevent carry-over contamination and it included a recombinant internal control to track for inhibitory reactions. Eleven out of the 45 cats were culture-positive, as revealed by microscopic identification of trichomonadid organisms. One of the isolates was subjected to scanning electron microscopy and findings revealed the presence of three flagella, thus placing the isolate into the gender Tritrichomonas sp. PCR and subsequent amplicon sequencing were carried out with ten of the 11 isolates. A total homology with published T. foetus sequences was confirmed in all of the cases. T. foetus therefore appears to range among those organisms that can cause chronic diarrhea in cats in Switzerland.

[Occurrence of Trichinella spp. in wild boar in Switzerland]

Trichinellosis is a worldwide occurring zoonosis caused by the intracellular nematode Trichinella spp. One of the main infection sources in Europe is raw or undercooked meat from wild boar. Trichinella britovi is prevalent in wild carnivores in Switzerland, thus a possible inclusion of wild boar in this wildlife cycle cannot be excluded. In order to assess the prevalence of Trichinella infection in wild boar, we tested 1,458 animals with both parasitological and serological methods. In none of the animals Trichinella-larvae could be recovered by the artificial digestion method (prevalence of larvae: 0 %; 95 % CI 0.0 - 0.3). Antibodies in meat juice were detected in 57 animals using a standardized E/S-Ag-ELISA. However, in the confirmatory westernblot, only 3 animals remained seropositive (seroprevalence: 0.2 %; 95 % CI 0.07 %-0.60 %). The occurrence of wild boar positive for anti-Trichinella-antibodies indicates that meat inspection for Trichinella-larvae in this species is important to prevent human infections.

Assessment of the prevalence of Trichinella spp. in red foxes and Eurasian lynxes from Switzerland

Trichinella spp. larvae have not been detected in Swiss pigs, horses, or wild boar for many decades, whereas the parasite was repeatedly isolated from red foxes and Eurasian lynxes. Whenever the isolated larvae could be subjected to genotyping, T. britovi was found as infective agent. The present study was initiated to re-assess the epidemiological situation of Trichinella infection in Swiss carnivorous wildlife, namely in red foxes and lynxes. Tissue samples from 1,298 foxes were collected between 2006 and 2007, and those of 55 lynxes between 1999 and 2007. All samples were tested by a standard artificial digestion method and a multiplex-PCR to determine the species and/or genotypes of recovered larvae. Trichinella larvae were found in 21 foxes (1.6%) and 15 lynxes (27.3%), and T. britovi was identified as infecting species in all cases. The geographic distribution of positive foxes showed two main clusters: one in Central Switzerland and one in the West of the country, where also many lynxes were found to be positive. While the prevalence for Trichinella infection in foxes was not statistically correlated with sex or age class, the prevalence in lynx was significantly higher in males compared to females, and in adults compared to juveniles.

Potentially human pathogenic Acanthamoeba isolated from a heated indoor swimming pool in Switzerland

Some free-living amoebae, including some species of the genus Acanthamoeba, can cause infections in humans and animals. These organisms are known to cause granulomatous amebic encephalitis (GAE) in predominantly immune-deficient persons. In the present study, we isolated a potentially human pathogenic Acanthamoeba isolate originating from a public heated indoor swimming pool in Switzerland. The amoebae, thermophilically preselected by culture at 37 degrees C, subsequently displayed a high thermotolerance, being able to grow at 42 degrees C, and a marked cytotoxicity, based on a co-culture system using the murine cell line L929. Intranasal infection of Rag2-immunodeficient mice resulted in the death of all animals within 24 days. Histopathology of brains and lungs revealed marked tissue necrosis and hemorrhagic lesions going along with massive proliferation of amoebae. PCR and sequence analysis, based on 18S rDNA, identified the agent as Acanthamoeba lenticulata. In summary, the present study reports on an Acanthamoeba isolate from a heated swimming pool suggestive of being potentially pathogenic to immunocompromised persons.

Unexplained gonad alterations in whitefish (Coregonus spp.) from Lake Thun, Switzerland: levels of persistent organic pollutants in different morphs

Since 2000, a surprisingly high number of macroscopical gonad alterations has been reported in whitefish (Coregonus spp.) from Lake Thun, Switzerland. This unique phenomenon is still unexplained and has received much public attention. As one possible trigger for these effects, the presence of persistent, bioaccumulative and toxic compounds acting as endocrine disruptors in the lake has been discussed. In this study, concentrations of selected persistent organic pollutants were examined in two morphs of whitefish from Lake Thun and their link to the observed abnormalities was investigated. Analyzed compound classes included polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins and dibenzofurans, polychlorinated naphthalenes, polybrominated diphenyl ethers and hexabromocyclododecanes. The target substances were identified in all samples and concentrations of the analyzed compounds were highly correlated among each other. These correlations show that the analyzed substances have the same distribution pattern throughout the lake and that uptake, accumulation and elimination processes are similar. Significant differences in contaminant levels within the samples existed between the two analyzed morphs of whitefish, most likely due to different age, food patterns and growth rate. No difference in contaminant levels was observed between fish with abnormal gonads and fish with normal gonads, suggesting no causal link between the investigated lipophilic organohalogen compounds present in fish and the observed gonad abnormalities in whitefish from Lake Thun. A comparison to existing data shows that concentrations in Lake Thun whitefish are at the lower bound of contaminant levels in whitefish from Swiss lakes or from European waters.

Appearance of red mark syndrome / cold water strawberry disease in Switzerland and Austria

Red mark syndrome (RMS) or cold water strawberry disease (CWSD) is a non-lethal skin disease of rainbow trout Oncorhynchus mykiss that is of high economic importance in the UK. The disease is temperature-dependent, with up to 60% morbidity at water temperatures below 15 degrees C. Although CWSD is horizontally transmissible, the aetiology is still unknown. Here we describe the first cases of RMS on the European mainland in the alpine regions of Switzerland and Austria. In Switzerland, morbidity remained around 1% after the first outbreak, whereas in Austria no further cases were diagnosed.