Salmonellosis in hospitalized horses: seasonality and case fatality rates

Salmonellosis was studied during an 11-year period (July 1971 through June 1982) in 245 hospitalized horses. Ten years' data (207 cases) were analyzed in a time series study. Peak seasonality of the disease was from June through September. The cycle curve revealed 3 major outbreaks, with no apparent periodicity. Eighteen Salmonella serotypes caused clinical salmonellosis in horses, but 84% of the cases and 90% of the deaths were caused by 5 serotypes: Salmonella typhimurium, S typhimurium var copenhagen, S anatum, S kottbus, and S saint-paul. Overall, the case fatality rate was 44.9%. Excluding mixed infections, horses infected with S typhimurium and S typhimurium var copenhagen, had a significantly higher (P less than 0.001) case fatality rate (60.4%) than those infected with other Salmonella serotypes (32.3%).     

THE PREVALENCE AND EPIZOOTIOLOGY OF SALMONELLOSIS AMONG GROUPS OF HORSES IN SOUTH EAST QUEENSLAND

Over a 3-year period, 1178 faecal samples were cultured from 462 horses admitted to the equine clinic of the University of Queensland; 185 samples were positive for salmonella yielding 213 isolations consisting of 21 serotypes. S. anatum was the predominant serotype isolated (54%) followed by S. ohio (11.27%) and S. typhimurium (9.4%). One hundred and ten horses (23.81%) were positive on one or more occasion, and 42 (9.09%) on more than one occasion.
S. anatum was the most common serotype isolated (71.43%) from the main drains in the stable block (33.57% positive samples).
The prevalence of salmonella excretors among a large non-clinic population of horses in south east Queensland was 1.65%.
Acute salmonellosis did not occur in the hospitalised animals. However, salmonellas were incriminated in 6 cases of chronic diarrhoea, which all yielded S. anatum , although the most severe involved both S. anatum and S. typhimurium , and these serotypes were isolated from multiple locations at the subsequent autopsy of 3 cases.     

Comparative plasmid profile analysis of Salmonella typhimurium var. Copenhagen strains from a Salmonella outbreak in hospitalized horses]

From April 1990 through June 1991 clinical salmonellosis and asymptomatic faecal excretion of Salmonella spp. were seen in hospitalized horses at two veterinary hospitals. 76 Salmonella strains from hospitalized horses and 18 strains from horses without any clinical contact were characterized by serotyping and plasmid profile analysis. From April 1990 through January 1991 97.8% of the hospitalized horses were infected with strains of S. typhimurium var. Copenhagen, which were closely related according to their similar plasmid patterns. Other strains of S. typhimurium var. Copenhagen and serotype S. enteritidis were isolated not before February 1991. In the same period various plasmid profile types of S. typhimurium var. Copenhagen and strains of S. typhimurium, S. enteritidis and S. lexington were isolated from horses of the control group. Our results suggest that the high incidence of salmonellosis and latent salmonella infection in hospitalized horses was mainly due to the spread of one particular strain of S. typhimurium var. Copenhagen and that this strain was obviously acquired during hospitalisation.     

The treatment of salmonellosis in Equidae.

Among 23 Equidae in which various treatment or management regimens for salmonellosis were observed and evaluated, 9 horses were infected with Salmonella typhimurium and 8 with S anatum; an aged mule harbored S newport, and 1 isolant was not identified. Four dual sero-type infections occurred: 3 typhimurium/anatum and 1 anatum/newington. The results obtained with various antimicrobials in therapy of peracute, acute, and chronic infections were discouraging or questionable with regard to efficacy against salmonellae per se. The antimicrobial resistance patterns of the salmonellae and coliforms from the same fecal sample of the patient were determined. Salmonellae cultured from feces prior to, during, and following treatment with a variety of drugs were often sensitive to the antimicrobial administered during these periods. Drug sensitivity or resistance appeared to have little, if any, bearing on eliminating salmonellae from the feces or organs of infected Equidae.     

Some aspects of the epidemiology of equine salmonellosis

A survey of 2 horse populations was done to detect the number of asymptomatic faecal excretors of Salmonella sp. 1201 faecal samples from 250 horses hospitalised at the University of Sydney were cultured. Three serotypes, S. typhimurium (4 horses), S. anatum (2) and S. tennessee (1) were isolated from 7 horses (2.8%). None was detected in 75 mares similarly examined at a thoroughbred stud farm. In retrospect, S. typhimurium was also the most common (70%) of the 19 serotypes recovered from 171 horses with clinical salmonellosis seen at Camden, 1969 to 1986. Forty cases occurring since 1983 were reviewed in detail; the mortality rate was high (60%) and an increased proportion was due to S. bovis-morbificans. Five horses developed salmonellosis while hospitalised and it was usually impossible to be certain whether these cases developed from the carrier state into overt disease or resulted from infections acquired in hospital.     

Protective effects of vaccines against experimental salmonellosis in racing pigeons

Five inactivated and one attenuated vaccine produced for the prevention of salmonellosis in pigeons were compared in an experimental challenge model. The birds were vaccinated according to the recommendations of the manufacturers and they were infected by gavage with a Salmonella typhimurium (var copenhagen) pigeon strain. The challenged control animals showed severe weight loss, excessive water intake over a prolonged period, and excreted large numbers of salmonellae. None of the vaccines fully protected the pigeons, and only an inactivated oil adjuvant vaccine was able to reduce the severity of the clinical signs significantly. Mortality was low and tended to increase with the severity of the clinical signs. These results do not justify the preventive use of salmonella vaccination in pigeons. Nevertheless, the oil adjuvant vaccine may help in the effective cleaning of lofts after an outbreak of salmonellosis.     

Effects of marketing stress on fecal excretion of Salmonella spp in feeder calves

Fecal samples were collected from 200 feeder-calves on farms in Tennessee, after assembly at a Tennessee auction market, and after transport to a Texas feedyard. A final fecal sample was collected from each calf after 30 days of feedyard confinement. The fecal samples were cultured for the presence of Salmonella spp. Salmonella isolates were serotyped and antimicrobial drug-resistance patterns determined. The number of calves fecal culture-positive for Salmonella spp increased from 0 on the Tennessee farms and auction market to 3/200 (1.5%) at entry into the Texas feedyard, and 16/200 (8%) after 30 days of feedyard confinement. Salmonella serotypes isolated and the number of isolates of each serotype were S reading (8), S cerro (4), S newbrunswick (3), S anatum (2), and S typhimurium (copenhagen; 2). All Salmonella isolates were resistant to 5 or more of 13 antimicrobial drugs tested. Salmonella reading isolates were resistant to 10 or 11 of 13 antimicrobial drugs. The results indicated that the calves could have been infected with Salmonella spp prior to or during the course of the study, and that marketing stress as they moved from farm through feedyard may have induced fecal excretion of salmonellae. In addition, the pattern of antimicrobial drug resistance in the Salmonella isolates was broad.     

The significance of the serotype in the clinical and pathological features of naturally occurring porcine salmonellosis.

Salmonellosis was the diagnosis in 63 of 327 consecutive porcine necropsy accessions during a one year period in Indiana, an incidence four to ten times that previously reported in other areas. A herd outbreak was usually either a septicemic disease characterized by sudden mortality. Little overlap between these two syndromes were seen. Animals dying with the septicemic form usually yielded Salmonella choleraesuis var. kunzendorf on culture. Salmonella typhimurium was the usual isolate from cases of enteric salmonellosis. Oral inoculation of SPF pigs with S. typhimurium resulted in a disease similar to naturally occurring enteric salmonellosis. The pathology of porcine salmonellosis due to S. typhimurium is described.     

Pleasure horses as a possible source of Salmonella agona

Horses in a riding stable sporadically excreted Salmonella agona, S anatum, and S newington in the feces. The three serotypes were isolated from apparently normal horses. The horses were sampled (the number sampled varied between 10 and 21) six times throughout a 13-month period. The greatest percentage of the horses (12 of 19, or 63%) were found to be excreting salmonella in September. Among the 12 horses excreting salmonella during this month, 8 (67%) were found to be excreting S agona.     

Transmissible antibiotic resistance in Salmonella isolated from random-source cats purchased for use in research.

Salmonella isolates from random-source cats designated for use in research were examined for antibiotic susceptibilities and the presence of plasmids containing R factors. The serotypes studied were Salmonella derby, S typhimurium, S anatum, S enteritidis, and S bredeney. Eighty percent of the isolates were resistant to one or more antibiotics. The greatest frequency of resistance was to streptomycin. The majority of the salmonella isolates transferred all or a part of their antibiotic resistance to an Escherichia coli K-12 recipient. Thermosensitive R factors were found in two S typhimurium isolates.     

OBSERVATIONS ON SALMONELLA INFECTIONS OF BIRDS

During the period 1961 to 1976, 29 species of Salmonella other than Salmonella pullorum were isolated from 180 accessions of birds examined at the Animal Research Institute, Yeerongpilly. These birds were submitted to the laboratory from flocks with disease or production problems. S. typhimurium was the most frequently isolated serotype being obtained from 63% of accessions. Outbreaks of systemic salmonellosis occurred most frequently in young birds and although pathological changes were most commonly observed in visceral organs they were also seen in eyes, joints and the brain. Diseases other than salmonellosis were identified in many accessions of birds with systemic or enteric salmonella infections.     

Salmonella infections in neonatal dairy calves.

To estimate herd prevalence of Salmonella spp, fecal specimens were obtained for culture from neonatal calves of 47 Ohio dairy herds. Of the 452 calves tested, 10 calves from 7 farms were culture-positive. Salmonella serotypes isolated were S dublin, S typhimurium, S enteritidis, S agona, S mbandaka, and S montevideo. Bulk tank milk filters from these dairies were also submitted for culture. Salmonella sp was isolated from 1 of the 50 filters, and 2 calves from this herd were found to be shedding Salmonella sp of the same serotype.     

Emergence of antibiotic-resistant Salmonella agona in horses in Kentucky

Eighty-seven of 283 isolates of salmonellae recovered from horses in Kentucky by the Livestock Disease Diagnostic Center from July 1, 1980 through June 30, 1984 were Salmonella agona. No isolations of S agona were made from Jan 1, 1972 through June 30, 1980. Salmonella agona was isolated from horses on 56 farms and most of the isolations were made in the spring. All age classes of horses were involved. Clinical forms of salmonellosis observed were diarrhea, septicemia, infertility, and abortion. Antibiotic susceptibilities were determined for 83 of the 87 isolates, and 79 were resistant to multiple antimicrobial agents, including chloramphenicol and gentamicin.     

Pathogenicity of different serogroups of avian salmonellae in specific-pathogen-free chickens.

The pathogenicity of one isolate of Salmonella typhimurium, four isolates of Salmonella heidelberg, three isolates of Salmonella kentucky, two isolates of Salmonella montevideo, one isolate of Salmonella hadar, and two isolates of Salmonella enteritidis (SE), one belonging to phage type (PT)13a and the other to PT34, was investigated in specific-pathogen-free chicks. Three hundred eighty-four chicks were separated into 16 equal groups of 24 chicks. Thirteen groups were inoculated individually with 0.5 ml of broth culture containing 1 x 10(7) colony-forming units (CFU) of either S. typhimurium (one source), S. heidelberg (four sources), S. montevideo (two sources), S. hadar (one source), S. kentucky (three sources), SE PT 13a (one source) or SE PT 34 (one source) by crop gavage. Two groups of 24 chicks were inoculated in the same way with 1 x 10(7) CFU of SE PT4 (chicken-CA) and Salmonella pullorum. Another group of 24 chicks was kept as an uninoculated control group. The chicks were observed daily for clinical signs and mortality. Isolation of salmonella was done from different organs at 7 and 28 days postinoculation (DPI). All the chicks were weighed individually at 7, 14, 21, and 28 DPI. Two chicks chosen at random from each group were euthanatized and necropsied at 7 and 14 DPI and all the remaining live chickens, at 28 DPI. Selected tissues were taken for histopathology at 7 and 14 DPI. Dead chicks were examined for gross lesions and tissues were collected for histopathology. Chicks inoculated with S. pullorum had the highest mortality (66.66%), followed by S. typhimurium (33.33%). Chicks inoculated with S. heidelberg (00-1105-2) and SE PT4 (chicken-CA) had 12.5% mortality and 8.3% mortality, respectively, with SE PT 13a. Ceca were 100% positive for salmonellae at acute or chronic infection compared with other organs. Mean body weight reduction ranged from 0.67% (inoculated with S. kentucky 00-926-2) to 33.23% (inoculated with S. typhimurium 00-372) in the inoculated groups at different weeks compared with uninoculated controls. Gross and microscopic lesions included peritonitis, perihepatitis, yolk sac infection, typhilitis, pneumonia, and enteritis in some groups, especially those inoculated with S. typhimurium, S. heidelberg (00-1 105-2), SE PT4 (chicken-CA), and S. pullorum.     

Characteristics of Salmonella isolated from animals at a veterinary medical teaching hospital

Salmonella belonging to 47 serotypes was isolated from animals at the University of California Veterinary Medical Teaching Hospital during the years 1974 to 1983. Salmonella belonging to 12 serotypes accounted for 89% of the 725 isolates. Salmonella typhimurium (including var copenhagen) was the most commonly isolated serotype, but during 1981 to 1983, S krefeld and S saint-paul were predominant. Certain serotypes seemed to be isolated more frequently from extraintestinal sources (S typhi-suis, S dublin). Although resistance to ampicillin, kanamycin, neomycin, streptomycin, and sulfonamides was common (greater than 60% of the isolates were resistant), resistance to chloramphenicol, gentamicin, and trimethoprim-sulfonamides was infrequent, except for isolates of S krefeld and S saint-paul.     

The prevalence of Salmonella infections in camels (Camelus dromedarius) in the United Arab Emirates.

One hundred and eighty-seven salmonella strains were isolated from 4006 samples collected from camels in the United Arab Emirates between 1987 and 1991. One hundred and sixty-five (4.3%) strains were isolated from 3801 faecal and 22 from 205 organ samples of 62 autopsied camels. In total, 28 different serotypes were identified with S. saintpaul being the most frequent (69), followed by S. frintrop (31) and S. hindmarsh (15). Salmonella typhimurium was isolated from only two faecal specimens. All salmonellas isolated from faecal samples originated from carrier camels, and those isolated from organs were secondary findings. The camels from which salmonella organisms were found died from diseases other than salmonellosis. Most of the S. saintpaul isolates originated from one herd suffering from Clostridium perfringens type A enterotoxaemia which suggests that salmonella infections may predispose camels to clostridial enterotoxaemias.     

Therapeutic trials with native intestinal microflora for Salmonella typhimurium infections in chickens

Chicks infected with Salmonella typhimurium at 1 day of age were treated with normal intestinal flora starting 3 or 9 days later. Chicks were reared on the floor in isolated pens with wood shavings for litter. Cloacal-swab cultures were the main criteria for determining S. typhimurium infection. A single treatment reduced the infection period, but multiple treatments hastened the process considerably: after 6-8 weeks, birds given multiple treatments yielded sporadic or no isolations of S. typhimurium. It appears that litter from birds colonized by a protective microflora may serve as a vehicle for transmitting the flora to succeeding groups of birds.     

Sources of salmonellae in an uninfected commercially-processed broiler flock.

Cultural monitoring was used to study the incidence and sources of salmonellae in a 4160 bird broiler flock during the growing period, transport and processing in a commercial plant. No salmonellae were isolated from any of 132 litter samples of 189 chickens cultured during the seven-week growing period, even though nest litter samples from four of the eight parent flocks yielded salmonellae and Salmonella worthington was isolated from the meat meal component of the grower ration. On arrival at the plant, 2/23 birds sampled carried S. infantis on their feathers, although intestinal cultures failed to yield salmonellae. Three of 18 processed carcasses samples yielded salmonellae (S. infantis, S. heidelberg, S. typhimurium var copenhagen). The most likely source of these salmonellae was the plastic transport crates, since 15/107 sampled before the birds were loaded yielded salmonellae (S. infantis, S. typhimurium). The crate washer at the plant did not reduce the incidence of Salmonella-contaminated crates, since 16/116 sampled after washing yielded salmonellae (S. infantis, S. typhimurium, S. heidelberg, S. schwarzengrund, S. albany).     

Comparison of rectal mucosal cultures and fecal cultures in detecting Salmonella infection in horses and cattle

Bacteriologic cultures of 65 rectal mucosal samples and 335 fecal samples from 53 horses and 5 cattle shedding Salmonella were performed. Salmonella spp were isolated from 34 (52%) rectal mucosal samples, 21 (32%) concurrent fecal samples, and 150 (45%) total fecal samples. The use of rectal mucosal samples when compared with concurrently obtained fecal samples significantly (P less than 0.025) improved the ability to isolate Salmonella spp. Concurrent bacteriologic culture of rectal mucosal samples and fecal samples resulted in 39 (60%) isolations. Compared with a series of fecal samples, Salmonella was isolated significantly more often when rectal mucosa and feces were cultured concurrently. Salmonella was isolated from rectal mucosal samples when it was not isolated from feces.     

Endothelial hyperpolarizing factor increases acetylcholine-induced vasodilatation in pulmonary hypertensive broilers arterial rings

Salmonellosis is an important disease of cattle caused predominantly by Salmonella enterica serotypes Typhimurium (S. typhimurium) and Dublin (S. dublin). S. typhimurium causes acute enteritis and exudative diarrhea in calves. In addition to enteric disease, S. dublin can cause systemic infections, and may cause abortion in pregnant cows. Calves are considered a relevant model for non-typhoidal salmonellosis in humans. Experimental oral infections or inoculation of ligated ileal loops in calves have been extensively studied recently. This article reviews relevant published results regarding bovine salmonellosis as a natural disease or as an animal model.