Salmonella Dublin infection in Queensland dairy cattle.

OBJECTIVE: To investigate the presence of Salmonella Dublin in Queensland cattle. DESIGN: An epidemiological study using diagnostic laboratory information and farm records. PROCEDURE: Outbreaks of gastroenteritis or pneumonia in calves, and abortions and enteritis in cows were routinely investigated for the presence of salmonellae. Where S Dublin was isolated, attempts were made to gather further epidemiological information. RESULTS: Prior to 1983 only two outbreaks of S Dublin have been recorded in Queensland dairy cattle. In 1983 S Dublin abortions were diagnosed in dairy heifers introduced from southern Australia to south-east Queensland. Sampling indicated that at least 10% of the 500 introduced heifers were faecal excretors of S Dublin. On 3 of the 7 farms from which S Dublin was recorded, infection spread to other cattle that were in contact. From February 1985 to February 1996, 29 outbreaks of S Dublin in cattle occurred on 29 farms (28 in south east Queensland and 1 in north Queensland). Calves were primarily affected. Continuing outbreaks were confirmed on only 4 of these 29 farms. On 15 farms S Dublin infections were associated with the purchase of infected calves or cows, while another farm adjoined 2 previously infected farms. No source of S Dublin was evident for the other 13 farms, where histories were often inadequate. CONCLUSION: There has been a marked increase in S Dublin outbreaks in Queensland dairy cattle since 1983. Introduction of S Dublin carrier and aborting dairy heifers from southern Australia, where S Dublin is not uncommon, was associated with the initial outbreaks.

Antimicrobial sensitivity testing of Australian isolates of Bordetella avium and the Bordetella avium-like organism.

The in-vitro sensitivity of 16 Australian isolates of Bordetella avium and 15 isolates of B avium-like organism to 11 antimicrobial agents or combinations of agents was determined using a microtitre plate system to establish minimal inhibitory concentrations. All the B avium isolates were sensitive to ampicillin but resistant to erythromycin, lincomycin, spectinomycin, sulphamethoxazole, trimethoprim, and lincomycin + spectinomycin. Most of the B avium isolates were sensitive to tetracycline and resistant to streptomycin and sulphadiazine. All the B avium-like isolates were resistant to ampicillin, erythromycin, lincomycin, spectinomycin, streptomycin, tetracycline, trimethoprim, and lincomycin+spectinomycin. Most B avium-like isolates were sensitive to sulphadiazine, sulphamethoxazole and trimethoprim-sulphamethoxazole.

A field evaluation of the polymerase chain reaction procedure for the detection of bovine leukaemia virus proviral DNA in cattle.

A polymerase chain reaction (PCR) procedure that detects proviral bovine leukaemia virus (BLV) in peripheral blood mononuclear cell DNA was evaluated. Blood samples from all animals (164) in a commercial dairy herd with a 30% prevalence of BLV infection, and from 194 animals from BLV free herds were tested. The absence of any positive PCR results in animals from BLV free herds confirmed the specificity of the assay. Initial testing of the infected herd using a single amplification PCR (SA-PCR), detected BLV infection in 62 of 72 adult animals that were seropositive by the agar gel immunodiffusion (AGID) test and in one persistently seronegative cow. Infection in this cow was confirmed by sheep bioassay. Subsequent testing of the SA-PCR negative, seropositive animals using a double amplification PCR (DA-PCR) detected proviral BLV in eight of nine animals that were available for retesting. The PCR assay was also able to distinguish BLV infected calves from uninfected calves that were serologically positive because of the presence of colostral antibody. Lymphocytes from all seropositive animals were cultured for determination of BLV antigen expression. Cultures from 37 of 62 SA-PCR positive animals produced detectable quantities of viral antigens. However, antigen expression was not detected in cultures from seropositive animals that were negative in the SA-PCR. In addition, in experimental transmission tests, inoculation of more than 10(6) lymphocytes from these cows was required for sheep to become seropositive to BLV.(ABSTRACT TRUNCATED AT 250 WORDS)

An evaluation of inactivated infectious coryza vaccines containing a double-emulsion adjuvant system.

The efficacy of experimental inactivated infectious coryza vaccines produced by a commercial vaccine manufacturer was evaluated. The vaccines, containing as the adjuvant phase either a double-emulsion mineral oil system or aluminum-hydroxide gel, were administered to 6-week-old chickens as a single dose. Some vaccines were a monovalent product containing a Page serovar C Haemophilus paragallinarum strain, and others were a bivalent product containing both Page serovar A and serovar C strains. After 3 weeks, all chickens were challenged by infraorbital sinus inoculation of virulent H. paragallinarum, either Page serovar C (strain HP31) or Page serovar A (strain HP14). The monovalent serovar C double-emulsion-based vaccines gave significant protection against a serovar C challenge, with the level of protection varying from 60% to 100%. The monovalent serovar C aluminum-hydroxide-gel vaccine also gave significant protection (94%) against a serovar C challenge. The bivalent double-emulsion vaccine gave significant protection against challenge from both serovars (100% for serovar C and 83% for serovar A). Although no major adverse reactions were detected, some chickens receiving both the double-emulsion vaccines and the aluminum-hydroxide vaccine developed relatively minor granulomatous reactions at the site of injection.

Comparison of Haemophilus paragallinarum isolates by restriction endonuclease analysis of chromosomal DNA.

Chromosomal DNA from Haemophilus paragallinarum was examined by restriction endonuclease analysis (REA) using the enzymes BamHI, EcoRI, HindIII, or SmaI. The enzyme SmaI had no apparent effect upon the DNA from eight representative H. paragallinarum isolates. The remaining enzymes cut the H. paragallinarum DNA to varying degrees, with the most useful patterns for distinguishing isolates being given by HindIII. The REA patterns given by HindIII were stable under both in vitro and in vivo conditions. The use of the enzyme HindIII showed that eight Australian isolates of H. paragallinarum were genetically similar. In contrast, 14 isolates of H. paragallinarum from outside Australia were markedly different from each other and the Australian isolates. A plasmid of approximately 6 kilobase pairs in size was found in one isolate of H. paragallinarum.

Serotyping of Haemophilus paragallinarum by the Page scheme: comparison of the use of agglutination and hemagglutination-inhibition tests.

Seventy-two isolates of Haemophilus paragallinarum were serotyped according to the Page scheme, using a new hemagglutination-inhibition (HI) test. The results were compared with the plate agglutination method conventionally used in the Page scheme. The HI test used washed cells of H. paragallinarum, glutaraldehyde-fixed chicken erythrocytes, and rabbit antisera originally produced for the agglutination method. For 49 of the isolates, there was complete correlation between the results of the HI serotyping test and the previously performed agglutination test--23 were serovar A, two were serovar B, and 24 were serovar C. The other 23 isolates were nontypable by the agglutination test, but 21 of them could be serotyped by the HI method--six as serovar A, two as serovar B, and 13 as serovar C. Nine isolates required treatment of the bacterial cells with hyaluronidase for the expression of hemagglutination (HA) activity. Two isolates did not have HA activity despite hyaluronidase treatment and so could not be serotyped by the HI test.

Proposal of a new serovar and altered nomenclature for Haemophilus paragallinarum in the Kume hemagglutinin scheme.

By using the Kume hemagglutinin serotyping scheme, 13 Australian isolates of Haemophilus paragallinarum were shown to constitute a new serovar within the presently termed serogroup II. Because of the likelihood that new serovars will continue to be established, we propose a rationalization of the nomenclature of the Kume scheme. Under this altered scheme, the three recognized serogroups I, II, and III are renamed A, C, and B, respectively. Within each of the serogroups, the serovars are numbered sequentially, allowing new serovars to be added in numerical order. Thus, the nine currently recognized Kume serovars are termed A-1, A-2, A-3, A-4, B-1, C-1, C-2, C-3, and C-4.

Epidemiologic studies on infectious coryza outbreaks in northern New South Wales, Australia, using serotyping, biotyping, and chromosomal DNA restriction endonuclease analysis.

The epidemiology of 16 cases of infectious coryza, an upper respiratory tract disease of chickens caused by Haemophilus paragallinarum, was investigated in a retrospective study. The cases occurred over a 14-month period on 10 farms in northern New South Wales. The available field data indicated that the cases formed six unrelated outbreaks. The 16 isolates of H. paragallinarum were subjected to serotyping by the Page and Kume schemes and biotyping based on carbohydrate fermentation and antimicrobial drug-resistance patterns. As well, newer fingerprinting techniques--plasmid profiles, whole-cell protein profiles, immunoblots of whole-cell protein profiles and total DNA restriction endonuclease analysis (REA)--were evaluated. Antimicrobial biotyping and REA profile typing proved most useful, allowing the recognition of three groups among the isolates. The other techniques gave either limited or no subdivision among the isolates. The combined results of the laboratory study indicated that, rather than six unrelated outbreaks, the 16 isolates represented three pairs of related outbreaks. This study represents the first application of sensitive biotyping and fingerprinting techniques to outbreaks of infectious coryza. The results have established that farms can be repeatedly infected with a single strain of H. paragallinarum that re-emerges at intervals. This study also obtained the first detailed evidence that replacement stock are a major source of infectious coryza.

The comparative pathogenicity of four serovars of Actinobacillus (Haemophilus) pleuropneumoniae.

The pathogenicity of 2 isolates of each of serovars 7, 3, 1 and 2 of Actinobacillus pleuropneumoniae was tested by intranasal inoculation into 60, 6-week-old large white pigs. Four dose rates varying from 0.27 to 560 x 10(6) organisms per pig with 10-fold serial dilutions were used. Surviving pigs were necropsied 7 days after inoculation. The proportion of pigs dying and developing gross lesions following infection was significantly greater for pigs given serotype 1 than for each of the other 3 serotypes, which did not differ significantly from each other. Twelve of 16 pigs given either of the 2 isolates of serovar 1 died after acute illness and 1 of 44 pigs given either of the 2 isolates each of serovars 7, 3 and 2 died. Pigs given serovar 1 showed high temperatures, severe respiratory distress, frothy haemorrhagic nasal discharge and weight loss. Lung lesions were produced in all 16 pigs given serovar 1, in 7 of 14 pigs given serovar 7, 7 of 14 pigs receiving serovar 3 and in 5 of 16 pigs given serovar 2. The lethal infections were characterised by a severe acute fibrinohaemorrhagic necrotising pleuropneumonia, whereas non-lethal cases had lung lesions ranging from necrotising purulent pleuropneumonia to abscessation. Significant differences between isolates in proportions of tissues culture positive for A. pleuropneumoniae for serovars 7 and 2, but not for serovars 3 and 1 suggested that isolates may vary in virulence within serovars, but more detailed studies are needed to clarify this point.

Biotyping of Haemophilus paragallinarum isolates using hemagglutinin serotyping, carbohydrate fermentation patterns, and antimicrobial drug resistance patterns.

Three techniques, a hemagglutinin (HA) serotyping scheme, carbohydrate fermentation patterns, and antimicrobial drug resistance patterns, were used to examine 92 isolates of Haemophilus paragallinarum. The results were used to create biotyping schemes. The carbohydrate fermentation and antimicrobial drug resistance patterns each resulted in the identification of five biovars. With both of these techniques, a large majority of the isolates fell into one biovar: 81% were biochemical biovar I and 73% were antimicrobial biovar I. However, by combining the results of these techniques with those of the HA serotyping, a much greater discrimination could be achieved. The combined use of hemagglutinin serotyping, biochemical biotyping and antimicrobial biotyping appears to provide a suitable approach for epizootiological studies on infectious coryza.

Comparison of hemagglutinin and agglutinin schemes for the serological classification of Haemophilus paragallinarum and proposal of a new hemagglutinin serovar.

Ninety-five isolates of Haemophilus paragallinarum were classified serologically by a hemagglutinin serotyping scheme, and the results were compared with results from agglutinin serotyping of the same isolates. Of the isolates, 65 were from Australia, 5 were from Japan, 6 were from the Federal Republic of Germany, 7 were from the United States, and 12 were from South Africa. Seven hemagglutinin serovars, HA-1 to HA-7, corresponding to agglutinin serovars A (HA-1, HA-2, and HA-3), C (HA-4, HA-5, and HA-6), and B (HA-7) have been described. Only one of the seven hemagglutinin serovars was found among the Australian isolates. This was serovar HA-5, comprising 49 isolates. Fifteen Australian isolates, all from southeast Queensland and northern New South Wales, were found to belong to a new hemagglutinin serovar. This was designated HA-8 and represented a fourth subgroup of agglutinin serovar A. Of the 95 isolates examined, only 1 did not produce a hemagglutinating antigen and was nonserotypeable by the hemagglutinin system. This compared favorably with the agglutinin scheme, which serotyped only 60 of the 95 isolates, with 29 nonserotypeable and 6 autoagglutinating.

Characterisation and antimicrobial sensitivity of haemophili isolated from pigs.

A total of 70 haemophili from Australia pigs was compared with a range of reference strains of porcine haemophili. Forty-eight of the isolates were identified as Actinobacillus pleuropneumoniae biovar 1 and the remaining 22 isolates as Haemophilus parasuis. Forty one of the A. pleuropneumoniae isolates were used in a study to determine to the minimal inhibitory concentration (MIC) of 12 antimicrobial agents, or combinations of agents. Penicillin, neomycin, trimethoprim, trimethoprim-sulphamethoxazole and tetracycline all showed low MIC values, indicating their potential for the treatment of porcine pleuropneumonia, although 2 isolates showed resistance to tetracycline. A wide range of MIC values was encountered with the sulphonamides.

Serological characterisation of Australian isolates of Actinobacillus pleuropneumoniae.

Using hyperimmune rabbit antiserums to 8 reference serovar strains, a total of 51 Australian isolates of Actinobacillus pleuropneumoniae were serotyped by either a rapid slide agglutination test or a gel diffusion test. The results were: serovar 1-24 isolates; serovar 2-6 isolates; serovar 3-5 isolates; serovar 7-15 isolates; nontypable-1 isolate. The rapid slide agglutination test was suitable for screening field isolates, as 73% of those tested reacted with only 1 of the 8 antiserums and were assigned to a particular serovar of the basis of this test alone.

Dieldrin poisoning and botulism in Australian pelicans (Pelecanus conspicillatus).

Autopsies and laboratory examinations of material from 24 Australian pelicans found sick or dead in southern coastal Queensland in 1977 to 1979 revealed dieldrin poisoning in 8 from the Brisbane region and botulism in 8 from Brisbane, Bundaberg and Gladstone. In those diagnosed as dieldrin poisoning, brain and liver samples contained 12.1 to 27.4 and 34.0 to 48.1 mg/kg dieldrin respectively. All of these birds were emaciated, 2 had convulsed and 1 had muscle tremors. Low and probably insignificant residues of DDE were detected in many birds. Type C botulism was confirmed in 4 of the 6 birds tested with specific antiserums. A large number of parasites including mites, lice, nematodes, cestodes, trematodes, coccidia and Sarcocystis sp were found but were thought to have had only a limited effect on the health of these birds.