Use of enzyme-linked immunoassays for antibody to types C and D botulinum toxins for investigations of botulism in cattle

Confirmation of botulism diagnosis in Australian bird samples by ELISA and RT rtPCR

We developed a sandwich ELISA that detects Clostridium botulinum C and D toxins and reverse-transcription real-time PCRs (RT-rtPCRs) that detect botulinum C and D toxin genes, respectively, to replace the mouse bioassay. The toxin genes were closely associated with the toxin molecules and used as surrogates for the presence of toxin. Samples (638) from 103 clinical cases of birds (302) with suspected botulinum toxicity came from wild birds and poultry (9 cases). Samples tested included blood serum, other body fluids, various tissues, gut contents, maggots, water, and sediment. Botulism was diagnosed in 34 cases (all of which had positive samples in the ELISA, the C toxin gene RT-rtPCR, or both assays). Botulism was suspected in 16 cases (each of which had 1 positive sample either in the ELISA or the C toxin gene RT-rtPCR). In the remaining 53 cases, no samples were positive, but botulism could not be excluded in 32 of these cases, whereas there was no indication of botulism or another diagnosis in 21 cases. The D toxin gene was not detected in any of the clinical samples. No C or D toxin genes were detected in 71 pooled cloacal swabs from 213 healthy migratory birds. The use of an ELISA that detects botulinum C and D toxins in combination with a RT-rtPCR for the botulinum C toxin gene can help confirm the diagnosis of botulism in birds.

Evidence for a natural humoral response in dairy cattle affected by persistent botulism sustained by non-chimeric type C strains

Bovine botulism is a sporadic acute disease that usually causes catastrophic losses in the herds. The unusual clinical evolution of a persistent mild outbreak in a dairy herd, prompted us to characterize the neurotoxin gene profile of the strain involved and to evaluate whether seroconversion had occurred. Diagnosis was based on mild classical symptoms and was supported by PCR and bacteriological findings, which revealed the involvement of a non-mosaic type C strain. An in-house ELISA was developed to detect antibodies to botulinum neurotoxin type C and its performance was evaluated in a vaccination study. Fifty days after the index case, fecal and serum samples were collected from the 14 animals of the herd and screened for Clostridium botulinum and anti-botulinum neurotoxin antibodies type C, respectively. The in-house developed ELISA was also used to test 100 sera samples randomly collected from 20 herds. Strong ELISA reactions were observed in 3 convalescent and 5 asymptomatic animals involved in the studied outbreak. The ELISA-positive cows all tested positive for non-mosaic C. botulinum type C in the feces and the same strain was also detected in the alfalfa hay, suspected to be the carrier source. Ten out of the 100 randomly collected sera tested positive for anti-botulinum neurotoxin type C antibodies: 7 had borderline values and 3 from the same herd showed titers three times higher than the cut-off. We concluded that type C botulism in cattle may occur with variable severity and that prolonged exposure to sublethal doses of botulinum neurotoxin C may occur, resulting in detectable antibodies.

Resposta humoral de bovinos vacinados contra as toxinas botulínicas tipos C e D em diferentes faixas etárias

Foi verificada pelo teste de ELISA indireto a resposta humoral contra os toxoides botulínicos C e D em bovinos de diferentes idades. O estudo envolveu 90 animais, que foram divididos em três grupos (n = 30), de acordo com a sua faixa etária; inferior a 2 anos de idade (G1), entre 2 e 5 anos (G2) e superior a 5 anos (G3). Os grupos experimentais foram vacinados com duas doses de vacina antibotulínica bivalente (C e D) comercial, nos dias 0 e 42 após a primo-vacinação (booster). Na avaliação, quando realizada 30 dias após o booster, os animais do G3 apresentaram maior produção de anticorpos (p < 0,05) em relação aos demais grupos. Entre o G1 e G2 não houve diferença significativa na resposta humoral contra a toxina C, no entanto, contra a toxina D, os animais do G1 apresentaram maior produção de anticorpos. Todos os grupos produziram uma resposta significativa de anticorpos contra as toxinas botulínicas após a 2ª dose da vacina bivalente comercial, principalmente contra o tipo D.

Shaping our future: animal health in a global trading environment

In this study, the clinical findings and results of haematological and biochemical analyses of 26 cattle with botulism were evaluated. The most important clinical signs in the affected cattle included: decreased appetite, ataxia, difficulty to rise, loss of tongue tone, salivation and bradycardia. A definitive diagnosis of botulism was based on demonstration of the preformed toxin in ruminal and intestinal contents and feed materials including poultry litter, by mouse inoculation test. This study is the first confirmation, by direct toxin isolation, of Clostridium botulinum type C and Clostridium botulinum type D in cattle, in Turkey.

Quantitative analysis of levels of serum immunoglobulin G against botulinum neurotoxin type D and association with protection in natural outbreaks of cattle botulism

The recent outbreaks of cattle botulism in vaccinated Israeli dairy cattle prompted us to determine vaccine efficacy and reasons for vaccine failure. Analysis of clinical signs, feeding practice, vaccination history, and epidemic curves enabled us to define a study population in two outbreaks, where high doses of Clostridium botulinum neurotoxin type D (BoNT/D) were evenly consumed by the affected animal groups. Attack rates among unvaccinated 6- to 24-month-old heifers were 96% (55/57) and 85% (53/62). The attack rates in vaccinated parity 1, 2, and >or=3 cows were 40.4% (21/52), 14.3% (4/28), and 5.6% (3/54), respectively. Vaccine efficacies for these cow groups were 52.5%, 83.2%, and 93.4%, respectively. In younger, unvaccinated 2- to 6-month-old calves, presumably protected by maternal antibodies, the attack rate was 24% (17/71). These differences correlated with significant differences in levels of specific anti-BoNT/D antibody in serum by an enzyme-linked immunosorbent assay (ELISA). The ELISA performance for predicting protection was analyzed by receiver operating characteristic analysis and was found to be highly significant, with an area under the curve of 0.941 (standard error, 0.034; 95% confidence interval, 0.875 to 1.008; P < 0.000). No animals with serum ELISA unit levels above 0.33 were affected in these exposed groups. At this cutoff level, the specificity of the ELISA was 100%, sensitivity was 67%, and accuracy was 92%. We concluded that botulinum toxoids can confer adequate protection against natural exposure to lethal doses of BoNT/D; however, the vaccination protocols should be optimized. Our in-house ELISA system will enable us to optimize vaccination protocols in the animal population.

Esporos e toxinas de Clostridium botulinum dos tipos C e D em cacimbas no Vale do Araguaia, Goiás

Foram avaliadas a ocorrência e distribuição de esporos e toxinas de Clostridium botulinum tipos C e D em 300 cacimbas empregadas como bebedouro de bovinos em 130 propriedades rurais localizadas em 12 municípios do Vale do Araguaia, Estado de Goiás. A presença de esporos foi determinada indiretamente pelo cultivo em meio de cultura, seguido da inoculação e neutralização em camundongo das amostras de sedimento do interior das cacimbas, e do solo superficial e fezes de bovinos, coletadas ao seu redor. A presença de toxina foi avaliada diretamente pela inoculação em camundongo do sedimento filtrado das cacimbas, também seguida da neutralização em camundongo com antitoxinas C e D. A presença de esporos de C. botulinum foi significativamente maior (p<0,05) nas fezes de bovinos (31%), quando comparadas com os resultados das amostras de solo superficial (19%) e dos sedimentos (10%). Foram detectadas toxinas botulínicas dos tipos C, D, ou classificadas como pertencentes ao complexo CD, em seis amostras (2%) das 300 cacimbas. Das 130 propriedades trabalhadas, em 122(93,85%) foram encontrados esporos ou toxinas de Clostridium botulinum em pelo menos uma das variáveis pesquisadas, enquanto somente 8(6,15%) não apresentaram qualquer contaminação A idade e profundidade das cacimbas estiveram associadas com a freqüência de detecção de esporos e toxinas. Assim, quanto mais velhas e rasas, maior a freqüência do isolamento de esporos e toxinas. A contaminação das cacimbas do Vale do Araguaia goiano com esporos e toxinas do Clostridium botulinum tipos C e D demonstra o risco potencial permanente e crescente para a ocorrência da intoxicação botulínica de origem hídrica nos bovinos.

Detection of type A, B, E, and F Clostridium botulinum neurotoxins in foods by using an amplified enzyme-linked immunosorbent assay with digoxigenin-labeled antibodies

An amplified enzyme-linked immunosorbent assay (ELISA) for the detection of Clostridium botulinum complex neurotoxins was evaluated for its ability to detect these toxins in food. The assay was found to be suitable for detecting type A, B, E, and F botulinum neurotoxins in a variety of food matrices representing liquids, solid, and semisolid food. Specific foods included broccoli, orange juice, bottled water, cola soft drinks, vanilla extract, oregano, potato salad, apple juice, meat products, and dairy foods. The detection sensitivity of the test for these botulinum complex serotypes was found to be 60 pg/ml (1.9 50% lethal dose [LD50]) for botulinum neurotoxin type A (BoNT/A), 176 pg/ml (1.58 LD50) for BoNT/B, 163 pg/ml for BoNT/E (4.5 LD50), and 117 pg/ml for BoNT/F (less than 1 LD50) in casein buffer. The test could also readily detect 2 ng/ml of neurotoxins type A, B, E, and F in a variety of food samples. For specificity studies, the assay was also used to test a large panel of type A C. botulinum, a smaller panel of proteolytic and nonproteolytic type B, E, and F neurotoxin-producing Clostridia, and nontoxigenic organisms using an overnight incubation of toxin production medium. The assay appears to be an effective tool for large-scale screening of the food supply in the event of a botulinum neurotoxin contamination event.

Clinical findings and treatment of 30 cattle with botulism

The clinical signs, the results of haematological and biochemical analyses and the treatment of 30 cattle with botulism are described, and the signs of the 13 cattle that survived are compared with those of the 17 that were euthanased owing to the disease. The cattle originated from 11 farms that had experienced an outbreak of botulism. The most important clinical sign in all the cattle was a reduction in the strength of the tongue; excessive salivation and difficulty in swallowing were observed in 20 of the animals, and the ears of 15 of them drooped. In 21 of the cattle, reaction to pricking of the head and body with a hypodermic needle was either absent or slight. Twelve of the animals had an unsteady, slow, difficult gait, and nine were unable to stand. A significantly higher proportion of the cattle which were euthanased had marked changes in behaviour and condition, anorexia, severely reduced skin turgor, weak tongues, a low rectal temperature, a high heart rate and a low blood pH; 11 were euthanased immediately after a clinical examination and six were euthanased one to five days after the initiation of treatment because their condition had deteriorated. Thirteen of the animals were treated for three to 23 days and were healthy when they were discharged. The treatment consisted of an intravenous infusion of 10 to 20 litres of glucose saline per day and the daily administration of fresh ruminal juice. Follow-up by telephone several months later revealed that all 13 animals had recovered completely.

Investigation of outbreaks of highly pathogenic H5N1 avian influenza in waterfowl and wild birds in Hong Kong in late 2002

Outbreaks of highly pathogenic H5N1 avian influenza have occurred in Hong Kong in chickens and other gallinaceous poultry in 1997, 2001, twice in 2002 and 2003. High mortality rates were seen in gallinaceous birds but not in domestic or wild waterfowl or other wild birds until late 2002 when highly pathogenic H5N1 avian influenza occurred in waterfowl (geese, ducks and swans), captive Greater Flamingo (Phoenicopterus ruber) and other wild birds (Little Egret Egretta garzetta) at two waterfowl parks and from two dead wild Grey Heron (Ardea cinerea) and a Black-headed Gull (Larus ridibundus) in Hong Kong. H5N1 avian influenza virus was also isolated from a dead feral pigeon (Columba livia) and a dead tree sparrow (Passer montanus) during the second outbreak. The first waterfowl outbreak was controlled by immediate strict quarantine and depopulation 1 week before the second outbreak commenced. Control measures implemented for the second outbreak included strict isolation, culling, increased sanitation and vaccination. Outbreaks in gallinaceous birds occurred in some live poultry markets concurrently with the second waterfowl outbreak, and infection on a chicken farm was detected 1 week after the second waterfowl park outbreak was detected, on the same day the second grey heron case was detected. Subsequent virus surveillance showed the outbreaks had been contained.

Clostridial disease associated with neurologic signs: tetanus, botulism, and enterotoxemia

Clostridial infections are found worldwide in almost all species of animals and may involve a variety of body systems and present with a diversity of clinical signs. Most damage done through clostridial infections is due to the action of toxins released from the bacteria.Thus, disease caused by Clostridium spp should more correctly be called intoxication. Two prominent clostridial infections are associated with neurologic signs: Clostridium botulinum and C tetani. In both infections, the mechanism that is responsible for causing the problem is similar, despite the remarkable difference in clinical presentation. In addition, neurologic signs are described with C perfringens types C and D but are not the dominant feature of these diseases.

Evaluation of a botulinum fragment C-based ELISA for measuring the humoral immune response in primates

An enzyme-linked immunosorbent assay (ELISA) using botulinum neurotoxin serotype B recombinant fragment C (rBoNTB(HC)) was developed to measure specific humoral immune responses of monkeys vaccinated with a vaccine consisting of rBoNTB(HC). Several fundamental parameters for a bioassay were evaluated. The evaluation results demonstrated that using BoNTB(HC) as the capture antigen led to a specific and sensitive ELISA for botulinum type B antibody with excellent precision, accuracy, and linearity. There was a good correlation (r=0.91) between ELISA titers and neutralization bioassay titers. Experimental results suggested that the ELISA could be useful for detecting botulinum type B antibody levels and may supplement mouse neutralization bioassays during planned clinical manufacturing and clinical trials of rBoNTB(HC) vaccine.

Suspected botulism in dairy cows and its implications for the safety of human food

A large outbreak of suspected botulism occurred on a dairy farm. The affected animals were listless and showed signs ranging from hindlimb unsteadiness to lateral recumbency, although the most common presentation was sternal recumbency with an apparent hindlimb weakness when stimulated to rise. Postmortem examinations revealed no conclusive gross pathology or histopathology. The affected cattle were found to have neutrophilia and hyperglycaemia with no other consistent haematological or biochemical abnormalities. The combination of clinical signs, disease epidemiology and the ruling out of other differential diagnoses strongly supported a diagnosis of unconfirmed botulism; however, the source of toxin was not demonstrated. Botulism is a severe disease in human beings and there are uncertainties about the pharmacokinetics and pharmacodynamics of Clostridium botulinum toxins. In such circumstances, a precautionary approach to food safety is essential. Restrictions were placed on the movement of livestock and sale of milk from the farm premises until 14 days after the onset of the last clinical case.

Comparative immunogenicity of two bivalent botulinum vaccines

OBJECTIVE

To compare the ability of a new single-dose botulinum vaccine containing a non-mineral oil adjuvant with a single dose of a conventional botulinum vaccine product to produce antibody to Clostridium botulinum types C and D in cattle in Northern Australia.

DESIGN AND PROCEDURE

One hundred and fifty Brahman steer weaners were randomly divided into two groups receiving either a single dose of CSL Bivalent Botulinum vaccine or Websters Singvac. Blood samples were collected at 0, 8 and 24 weeks and tested by antibody ELISA. The final samples were also tested by the toxin neutralisation test, to test titres of neutralising antibody.

RESULTS

Six months after inoculation, cattle vaccinated with Websters Singvac had ELISA antibody response twice that of CSL conventional product. However, this difference was only evident for neutralising antibody to type C botulinum toxin. Both products produced similar titres of type D neutralising antibody after a single dose.

CONCLUSION

Websters' Singvac produces a greater neutralising antibody response to type C botulism upon single inoculation than a conventional vaccine. The product produces an equivalent neutralising antibody response to type D.

A multiple antigen ELISA to detect Neospora-specific antibodies in bovine sera, bovine foetal fluids, ovine and caprine sera

Neospora caninum is a cyst-forming coccidian parasite recently identified as a cause of abortion in cattle. The epidemiology of neosporosis is poorly understood, partly because accurate diagnosis of infection is difficult. In this paper we describe the development of a multiple antigen-based enzyme-linked immunosorbent assay (ELISA) to detect antibodies to N. caninum in sera from cattle, sheep and goats as well as from bovine foetal fluids. A water-soluble fraction (wsf) of sonicated NC-1 strain tachyzoites was used as the antigen in the ELISA. Minimum optical density (OD) values that were considered to be Neospora antibody-positive, that is, the cut-off OD values were determined separately for bovine maternal sera, bovine foetal fluids, ovine sera and caprine sera; they were 0.40, 0.17, 0.23 and 0.41 OD, respectively. The ELISA gave a high signal/noise ratio, giving good sensitivity and specificity, correlating well with the indirect fluorescent antibody test (IFAT) currently used to diagnose Neospora infection in cattle, sheep and goats. In both the ELISA and immunoblot analysis using the same antigen, there was no significant cross-reactivity with sera from cattle, sheep or goats that had been infected with Toxoplasma gondii. The ELISA also showed no cross-reactivity in sera from cattle infected with Sarcocystis cruzi, Babesia divergens, B. bovis and B. bigemina. The wsf fraction of sonicated N. caninum tachyzoites used in this ELISA can be easily prepared and may be more sensitive than a single antigen ELISA, whilst still retaining good specificity.

Botulism

Equine botulism is being recognized with increasing frequency by veterinarians throughout North America. Muscular weakness and dysphagia that progress during a period of 1 to 4 days, in the absence of laboratory derangements that indicate the presence of systemic disease, are suggestive of botulism. A tentative diagnosis usually is based on the presence of the following findings on physical examination: delayed pupillary light response, mydriasis, ptosis, generalized weakness, decreased tail tone, and slow prehension of feed. Definitive diagnosis requires detection of botulinum toxin in plasma, serum, gastrointestinal contents, or body tissues. Early treatment with antitoxin generally results in a favorable outcome. Botulism in foals and adult horses can be prevented by vaccination.