Type A botulism in horses in the United States: a review of the past ten years (1998-2008)

Diagnosis of botulism in mammals aided by toxin ELISA and C and D gene RT-PCRs with an emphasis on farm animals

Animal welfare and ethical considerations limit the use of the mouse lethality bioassay for the detection of botulinum toxins. This study assessed an ELISA and RT-PCRs to detect toxin types C and D in samples from mammals with flaccid paralysis or weakness. DNA/RNA tightly bound to the toxin molecules were used as surrogates for the presence of toxin. In total 391 diverse samples from 101 clinical cases from cattle and 9 other species were examined. Botulism was confirmed by ELISA in samples from 16 cases. Toxin type C or D was identified by RT-PCR in 10 cases, five of which were among the cases confirmed by ELISA. Among the 80 cases with negative samples, sampling was not comprehensive enough in 66 cases (botulism therefore not excluded) but was adequate in 14 cases (no indication of botulism). The last two categories included 16 cases with other laboratory findings explaining the clinical signs. The ELISA that detects botulinum C and D toxins was superior in identifying cases with positive samples compared to the RT-PCRs but the latter were able to identify the toxin type present when positive. Furthermore, the RT-PCRs are available to any laboratory with molecular testing capability. Both laboratory assays can screen a comprehensive range and a large number of samples which is crucial for a successful diagnosis of botulism.

Characterizing hay buying and feeding practices and attitudes among Pennsylvania horse owners

Existing data on the equine hay market and buying preferences in Pennsylvania (PA) is outdated and more recent data is needed. The objective of this project was to characterize the practices and attitudes of PA horse hay buyers. An online survey was created and distributed. It received 435 total responses (of these, 346 were complete responses) from PA horse hay buyers from October 2021 to February 2022. Data presented (descriptive statistics) represents the percentage of respondents answering that question. Most (76%) respondents were in the recreational sector of the horse industry and the majority (62%) purchased hay for 2-5 horses. Small square bales (2-string) were most commonly purchased (93%), and most respondents bought their hay exclusively by the bale (75%). The most common reasons for not purchasing large bales were not being able to transport or handle them (70%), followed by not having adequate storage (60%). Horse owners were most likely to buy hay directly from local farmers (90%) than any other source. The top three most important factors when purchasing hay were absence of mold, absence of weeds, and smell (rated "very important" by 98, 53, and 52% of respondents, respectively). Most respondents did not use hay feeders in stalls or outside (38 and 50%, respectively). Most hay buyers (63%) never have their hay analyzed for nutrient content. The data collected from this survey can help hay producers understand buying practices of horse owners and help equine nutritionists identify areas of need for horse owner education about hay.

Antimicrobial Resistance in Equines: A Growing Threat to Horse Health and Beyond-A Comprehensive Review

The equine industry holds substantial economic importance not only in the USA but worldwide. The occurrence of various infectious bacterial diseases in horses can lead to severe health issues, economic losses, and restrictions on horse movement and trade. Effective management and control of these diseases are therefore crucial for the growth and sustainability of the equine industry. While antibiotics constitute the primary treatment strategy for any bacterial infections in horses, developing resistance to clinically important antibiotics poses significant challenges to equine health and welfare. The adverse effects of antimicrobial overuse and the escalating threat of resistance underscore the critical importance of antimicrobial stewardship within the equine industry. There is limited information on the epidemiology of antimicrobial-resistant bacterial infections in horses. In this comprehensive review, we focus on the history and types of antimicrobials used in horses and provide recommendations for combating drug-resistant bacterial infections in horses. This review also highlights the epidemiology of antimicrobial resistance (AMR) in horses, emphasizing the public health significance and transmission dynamics between horses and other animals within a One Health framework. By fostering responsible practices and innovative control measures, we can better help the equine industry combat the pressing threat of AMR and thus safeguard equine as well as public health.

Application and Future Prospective of Lactic Acid Bacteria as Natural Additives for Silage Production—A Review

Ensiling is one of the essential processes to preserve fodder with high nutrients and microbiological quality. The forages before ensiling have a limited number of bacteria associated with the controlled fermentation process. Undesirable microbes can grow in silages when there is not efficient fermentation. Such kinds of microbes might cause pathogenic or toxic compounds that affect animal and human health. Therefore, it is necessary to inoculate potent starter cultures. Lactic acid bacteria’s (LABs) have been considered the most prominent microbial additives used to improve the quality of silage. Currently, LABs have been used in modern and sustainable agriculture systems due to their biological potential. Recently, many scientists have increased their focus on developing nutrient-rich animal feed from forages with LAB. This current review focuses on issues related to forage preservation in the form of silages, how undesirable microbes affect the fermentation process, the critical role of LAB in silage production, and the selection of potent LABs to effectively control unwanted microbial growth and promote those which favor animal growth.

Modification and validation of the Endopep-mass spectrometry method for botulinum neurotoxin detection in liver samples with application to samples collected during animal botulism outbreaks

Botulinum neurotoxins (BoNTs) are the most potent toxins known and they cause the paralytic disease botulism in humans and animals. In order to diagnose botulism, active BoNT must be detected in biological material. Endopep-MS is a sensitive and selective method for serum samples, based on antibody capture, enzymatic cleavage of target peptides, and detection of cleavage products using matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS). In many cases of animal botulism, serum samples are not available or they do not contain detectable amounts of BoNT and liver sampling is an alternative for postmortem examinations. However, the Endopep-MS method is impaired by the inherent protease activity of liver samples. In the presented study, the Endopep-MS method has been successfully modified and validated for analysis of cattle, horse, and avian liver samples, introducing a combination of a salt washing step and a protease inhibitor cocktail. These modifications resulted in a substantial decrease in interfering signals and increase in BoNT-specific signals. This led to a substantial improvement in sensitivity for especially BoNT-C and C/D which are among the most prominent serotypes for animal botulism. Botulism was diagnosed with the new method in liver samples from dead cattle and birds from outbreaks in Sweden. Graphical Abstract.

Outbreak of botulism type A in dairy cows detected by MALDI-TOF mass spectrometry

Twenty-eight lactating dairy cattle in New York State were exposed to botulism toxin; 12 died and 16 recovered but never returned to full productivity. Pieces of a raccoon carcass were found in the total mixed ration on the first day of the outbreak. Clinical signs included anorexia, decreased milk production, decreased tongue tone, profound weakness, and recumbency. Clostridium botulinum type A (BoNT/A) was detected in rumen contents from 2 deceased cows via matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). In addition, C. botulinum type C was cultured from the liver of a third cow, and C. botulinum neurotoxin-producing type C gene (bont/C) was detected via real-time PCR. On postmortem examination, 4 cows had findings suggestive of toxic myopathy, but the cause and significance of these lesions is unknown given that botulism is typically not associated with gross or histologic lesions. This outbreak of BoNT/A in cattle in North America was diagnosed via MALDI-TOF MS, a rapid and sensitive modality for detection of botulinum preformed neurotoxin.

Public Health Risk Associated with Botulism as Foodborne Zoonoses

Botulism is a rare but severe neurological disease in man and animals that is caused by botulinum neurotoxins (BoNTs) produced by Clostridium botulinum and atypical strains from other Clostridium and non-Clostridium species. BoNTs are divided into more than seven toxinotypes based on neutralization with specific corresponding antisera, and each toxinotype is subdivided into subtypes according to amino acid sequence variations. Animal species show variable sensitivity to the different BoNT toxinotypes. Thereby, naturally acquired animal botulism is mainly due to BoNT/C, D and the mosaic variants CD and DC, BoNT/CD being more prevalent in birds and BoNT/DC in cattle, whereas human botulism is more frequently in the types A, B and E, and to a lower extent, F. Botulism is not a contagious disease, since there is no direct transmission from diseased animals or man to a healthy subject. Botulism occurs via the environment, notably from food contaminated with C. botulinum spores and preserved in conditions favorable for C. botulinum growth and toxin production. The high prevalence of botulism types C, D and variants DC and CD in farmed and wild birds, and to a lower extent in cattle, raises the risk of transmission to human beings. However, human botulism is much rarer than animal botulism, and botulism types C and D are exceptional in humans. Only 15 cases or suspected cases of botulism type C and one outbreak of botulism type D have been reported in humans to date. In contrast, animal healthy carriers of C. botulinum group II, such as C. botulinum type E in fish of the northern hemisphere, and C. botulinum B4 in pigs, represent a more prevalent risk of botulism transmission to human subjects. Less common botulism types in animals but at risk of transmission to humans, can sporadically be observed, such as botulism type E in farmed chickens in France (1998-2002), botulism type B in cattle in The Netherlands (1977-1979), botulism types A and B in horses, or botulism type A in dairy cows (Egypt, 1976). In most cases, human and animal botulisms have distinct origins, and cross transmissions between animals and human beings are rather rare, accidental events. But, due to the severity of this disease, human and animal botulism requires a careful surveillance.

The First Case of Botulism in a Donkey

Botulism, a severe neuroparalytic disease that can affect humans, all warm-blooded animals, and some fishes, is caused by exotoxins produced by ubiquitous, obligate anaerobic, spore-forming bacteria belonging to the genus Clostridium and named botulinum neurotoxin (BoNT)-producing clostridia. This report presents the case of a 3-year-old donkey mare referred for progressive and worsening dysphagia of four days’ duration. Her voluntary effort in eating and drinking was conserved, and she was able to slow chew without swallowing. A complete neurological examination was performed, and botulism was strongly suspected. The ability to swallow feed and water returned on the tenth day of hospitalization and improved progressively. The jenny was discharged from the hospital after fifteen days. During the hospitalization, the Italian National Reference Centre for Botulism confirmed the diagnosis: mare’s feces were positive for BoNT/B and Clostridium botulinum type B.

Accuracy of a Mouse Bioassay for the Diagnosis of Botulism in Horses

Background

The laboratory diagnosis of botulism in horses traditionally has relied upon the mouse bioassay (MBA). The accuracy of this test for the diagnosis of botulism in horses is unknown.

Hypothesis/Objectives

Our goal was to determine the sensitivity, specificity, positive predictive value, and negative predictive value of the MBA on laboratory‐processed fecal and gastrointestinal samples for foals and adult horses.

Animals

Cases included all horses with a final clinical diagnosis of botulism that were admitted between 1986 and 2011 and had MBA testing performed. Controls included horses without botulism that were admitted during the same time period and had MBA testing performed.

Methods

Retrospective study. Horses suspected of having botulism had fecal or (less commonly) gastrointestinal content samples tested using MBA. For every hospitalized botulism suspect, control samples were obtained from ≥1 additional hospitalized horses not suspected to have botulism.

Results

One hundred and twenty‐nine adult horses and 253 adult controls were identified. Overall sensitivity of the MBA was only 32% but specificity was 97%. Forty‐three foal cases and 21 foal controls were evaluated; sensitivity of the MBA was 53% and specificity was 100%. Positive predictive value was substantially higher (100% for foals and 89% for adults) than negative predictive value (51% for foals and 67% for adults).

Conclusions and Clinical Importance

Mouse bioassay has low sensitivity but high specificity for the diagnosis of botulism in horses. Positive results are highly suggestive of botulism but negative results do not exclude the diagnosis. Unaffected horses and foals rarely shed C. botulinum in their feces.

Botulism (type A) in a horse - case report

This paper presents the case of a six year-old, male, thoroughbred horse with clinical signs of inappetence, weakness, and incoordination when walking. Clinical examination showed that the horse staggered and leaned to the left side. Feedstuff was present inside and around its mouth. Salivation was increased and there was no reflex at the palpebrae and tongue. The horse had difficulty swallowing and the tone of its tail was reduced. Botulism was diagnosed based on the clinical signs. Antibiotic (ceftiofur) and fluid-electrolyte treatment was commenced. Next day, neostigmin was added to the horse’s treatment, and it became recumbent. The horse’s palpebral, tongue and tail reflexes returned partially after neostigmine methylsulphate treatment on the same day and it stood up on day four. However, it could not swallow anything during the whole week, so after getting permission from the owner, the horse was euthanized on day 10. Samples of the colonic content and blood serum were sent by courier to the laboratory for toxin neutralization, however, botulinum neurotoxins could not be detected. After that, serum samples from days 6 and 10 were sent to another laboratory for testing for botulinum neurotoxin antibodies by ELISA. Specific antibodies against botulinum neurotoxin type A were measured, indicating a previous, immuno-relevant contact with the toxin. This seroconversion for type A supports the clinical botulism diagnosis. Type A botulism is rarely seen in Europe and has been detected in a horse in Turkey for the first time.

Gorilla gorilla gorilla gut: a potential reservoir of pathogenic bacteria as revealed using culturomics and molecular tools

Wild apes are considered to be the most serious reservoir and source of zoonoses. However, little data are available about the gut microbiota and pathogenic bacteria in gorillas. For this propose, a total of 48 fecal samples obtained from 21 Gorilla gorilla gorilla individuals (as revealed via microsatellite analysis) were screened for human bacterial pathogens using culturomics and molecular techniques. By applying culturomics to one index gorilla and using specific media supplemented by plants, we tested 12,800 colonies and identified 147 different bacterial species, including 5 new species. Many opportunistic pathogens were isolated, including 8 frequently associated with human diseases; Mycobacterium bolletii, Proteus mirabilis, Acinetobacter baumannii, Klebsiella pneumoniae, Serratia marcescens, Escherichia coli, Staphylococcus aureus and Clostridium botulinum. The genus Treponema accounted for 27.4% of the total reads identified at the genus level via 454 pyrosequencing. Using specific real-time PCR on 48 gorilla fecal samples, in addition to classical human pathogens, we also observed the fastidious bacteria Bartonella spp. Borrelia spp., Coxiella burnetii and Tropheryma whipplei in the gorilla population. We estimated that the prevalence of these pathogens vary between 4.76% and 85.7%. Therefore, gorillas share many bacterial pathogens with humans suggesting that they could be a reservoir for their emergence.

Outcome of adult horses with botulism treated at a veterinary hospital: 92 cases (1989-2013)

Background

There are no studies evaluating a large population of adult horses treated for botulism. Reported survival rates in outbreak situations are low; however, many horses in outbreaks do not receive treatment.

Hypothesis/Objectives

That adult horses treated at a veterinary hospital would have improved survival compared to outbreak situations. Additional aims included identification of predictors of nonsurvival.

Animals

All horses greater than 6 months of age with a final diagnosis of botulism admitted to a veterinary teaching hospital between 1989 and 2013 were included.

Methods

Retrospective study. Historical, admission, and hospitalization data were retrieved from medical records and associations between variables and nonsurvival were identified using logistic regression. Two multivariable models were developed pertaining to (1) information available at admission and (2) clinical findings during hospitalization.

Results

Ninety‐two records met inclusion criteria. Retained variables for the two models indicated that higher rectal temperature (OR, 1.94; CI, 1.19–3.17) and dysphagia (OR, 4.04; CI, 1.01–16.17) observed at admission increased the odds of survival, as did treatment with antitoxin (OR, 121.30; CI, 9.94–1,480.65). Horses with abnormal respiratory effort or inability to stand had decreased odds of survival. Overall survival was 48% but was significantly higher (67%, P = .011) for horses that arrived standing, and even higher (95%, P < .001) for horses that remained able to stand throughout hospitalization. Complications occurred in 62% of horses but were not associated with nonsurvival.

Conclusions and Clinical Importance

Horses that lose the ability to stand have a poor chance of survival. Complications are common in treated horses but do not reduce survival.

Mechanical ventilation and management of an adult horse with presumptive botulism

OBJECTIVE

To describe the clinical course, management, and outcome of a horse with a presumptive diagnosis of botulism treated with long-term mechanical ventilation.

CASE SUMMARY

A 6-year-old Quarter Horse gelding with a history of esophageal obstruction was evaluated for progressive tetraparesis. Generalized and progressive skeletal muscle weakness characterized by recumbency, decreased tongue, tail, eyelid, and anal tone, and respiratory failure was observed. Anticholinergic signs including decreased salivation, xerophthalmia, and ileus were also noted. A presumptive diagnosis of botulism was made, although mouse inoculation and spore identification testing were negative. Pentavalent botulism antitoxin was administered on Day 3. The horse was maintained on a water mattress and was managed with mechanical ventilation for 2 weeks. Complications encountered included necrotic rhinitis, intertrigo, decubital ulceration, jugular and cephalic vein thrombophlebitis, corneal ulceration, and transient ventricular tachycardia. The horse showed marked improvement in skeletal muscle strength and parasympathetic nervous system function, allowing it to be successfully weaned from the ventilator but suffered large colon volvulus on Day 21 and was euthanized.

NEW OR UNIQUE INFORMATION PROVIDED

To the authors' knowledge, this is the first report of successful weaning from long-term mechanical ventilation and management of recumbency using a water mattress in an adult horse with presumptive botulism.

Multiplex real-time PCR for detecting and typing Clostridium botulinum group III organisms and their mosaic variants

Botulism is a neuroparalytic disease that can occur in all warm-blooded animals, birds, and fishes. The disease in animals is mainly caused by toxins produced by Clostridium botulinum strains belonging to group III, although outbreaks due to toxins produced by group I and II organisms have been recognized. Group III strains are capable of producing botulinum toxins of type C, D, and C/D and D/C mosaic variants. Definitive diagnosis of animal botulism is made by combining clinical findings with laboratory investigations. Detection of toxins in clinical specimens and feed is the gold standard for laboratory diagnosis. Since toxins may be degraded by organisms contained in the gastrointestinal tract or may be present at levels below the detection limit, the recovery of C. botulinum from sick animal specimens is consistent for laboratory confirmation. In this article we report the development and in-house validation of a new multiplex real-time PCR for detecting and typing the neurotoxin genes found in C. botulinum group III organisms. Validation procedures have been carried out according to ISO 16140, using strains and samples recovered from cases of animal botulism in Italy and France.

Management of animal botulism outbreaks: from clinical suspicion to practical countermeasures to prevent or minimize outbreaks

Botulism is a severe neuroparalytic disease that affects humans, all warm-blooded animals, and some fishes. The disease is caused by exposure to toxins produced by Clostridium botulinum and other botulinum toxin-producing clostridia. Botulism in animals represents a severe environmental and economic concern because of its high mortality rate. Moreover, meat or other products from affected animals entering the food chain may result in a public health problem. To this end, early diagnosis is crucial to define and apply appropriate veterinary public health measures. Clinical diagnosis is based on clinical findings eliminating other causes of neuromuscular disorders and on the absence of internal lesions observed during postmortem examination. Since clinical signs alone are often insufficient to make a definitive diagnosis, laboratory confirmation is required. Botulinum antitoxin administration and supportive therapies are used to treat sick animals. Once the diagnosis has been made, euthanasia is frequently advisable. Vaccine administration is subject to health authorities' permission, and it is restricted to a small number of animal species. Several measures can be adopted to prevent or minimize outbreaks. In this article we outline all phases of management of animal botulism outbreaks occurring in wet wild birds, poultry, cattle, horses, and fur farm animals.

Infection control and biosecurity in equine disease control

Infectious diseases are an important cause of morbidity and mortality in horses, along with economic costs and broader impacts associated with the loss of members of a species that generates income, acts as a working animal and is a companion. Endemic diseases continue to challenge, emerging diseases are an ever‐present threat and outbreaks can be both destructive and disruptive. While infectious diseases can never be completely prevented, measures can be introduced to restrict the entry of pathogens into a population or limit the implications of the presence of a pathogen. Objective research regarding infection control and biosecurity in horses is limited, yet a variety of practical infection prevention and control measures can be used. Unfortunately, infection control can be challenging, because of the nature of the equine industry (e.g. frequent horse movement) and endemic pathogens, but also because of lack of understanding or motivation to try to improve practices. Recognition of the basic concepts of infection control and biosecurity, and indeed the need for measures to control infectious diseases, is the foundation for successful infection prevention and control.

Quantitative real-time PCR for detection of the neurotoxin gene of Clostridium botulinum type B in equine and bovine samples

Clostridium botulinum type B is estimated to cause more than 85% of cases of equine botulism in the United States, as well as many outbreaks in cattle. In this study, a quantitative real-time polymerase chain reaction for detection of the neurotoxin gene of C. botulinum type B was compared to the mouse bioassay using 45 positive and 43 negative samples of equine, bovine or associated environmental origin. The sensitivity of the qPCR assay was 96%, whereas the sensitivity of the mouse bioassay was 84%. The specificity of the qPCR assay was 95% and the specificity of the mouse bioassay was 100%.

An outbreak of equine botulism type A associated with feeding grass clippings

In September 2010, an outbreak of type A botulism involved 4 horses in northern California that were fed grass clippings obtained from a nearby park. All 4 animals developed a progressive flaccid paralysis syndrome clinically consistent with exposure to preformed Clostridium botulinum neurotoxin (BoNT). Within 48 hr of consuming the grass clippings, all 4 horses showed marked cervical weakness (inability to raise their heads to a normal position) and died or were euthanized within 96 hr. One horse was submitted for diagnostic examination and subsequent necropsy. At necropsy, extensive edema was observed in areas of the nuchal ligament and inguinal fascia. A sample of the grass clippings tested positive for preformed BoNT type A by the mouse bioassay test. Emphasis should be placed on early case recognition, rapid initiation of treatment with the trivalent antitoxin product, and preventing exposure to BoNT in spoiled forages.

Toxins and adverse drug reactions affecting the equine nervous system

This article provides an overview of the more common toxins and adverse drug reactions, along with more rare toxins and reactions (Table 1), that result in neurologic dysfunction in horses. A wide variety of symptoms, treatments, and outcomes are seen with toxic neurologic disease in horses. An in-depth history and thorough physical examination are needed to determine if a toxin or adverse drug reaction is responsible for the clinical signs. Once a toxin or adverse drug reaction is identified, the specific antidote, if available, and supportive care should be administered promptly.

Miscellaneous neurologic or neuromuscular disorders in horses

NMD is an important cause of morbidity in horses. Signs of dysfunction could be variable depending on the specific area affected. NM disease can go unrecognized if a thorough evaluation is not performed in diseased horses. Electrodiagnostic testing is an area that has the potential to document and improve our understanding of NM disease yet is uncommonly performed. Keeping an open and observant mind will enhance our ability to search and find answers.