Efficacy of Two Probiotic Products Fed Daily to Reduce Clostridium perfringens-Based Adverse Health and Performance Effects in Dairy Calves

Clostridium perfringens is a spore-forming, anaerobic bacterium which produces toxins and exoenzymes that cause disease in calves, especially necro-hemorrhagic enteritis-associated diarrhea often resulting in death. Clostridium infections are currently being treated with antibiotics, but even with the prudent administration of antibiotics, there are significant rates of recurrence. Probiotics, an alternative to antibiotics, are commonly employed to prevent clostridial infections. The objectives of our study were to demonstrate that two commercially available products, when used as daily, direct-fed microbials, are effective in reducing adverse effects of an experimentally induced C. perfringens infection in dairy calves. We conducted a single site efficacy study with masking using a randomized design comprising 10 calves allocated to 3 treatment groups (probiotic 1, probiotic 2, and control). The procedures such as general health scores, body weight, blood samples, and fecal sample collections were done followed by experimental challenge of calves with C. perfringens. Daily feeding of L. animalis LA51 and P. freudenreichii PF24 without or with Bacillus lichenformis CH200 and Bacillus subtilis CH201, before, during and after an oral challenge of C. perfringens significantly reduced the incidence and severity of diarrhea while improving general impression and appearance scores of calves. Most notably, survival of calves in the two probiotic-fed groups was significantly higher than for control calves and further substantiates the potential economic and health benefits of feeding effective probiotics.

Pathology and Pathogenesis of Brain Lesions Produced by Clostridium perfringens Type D Epsilon Toxin

Clostridium perfringens type D epsilon toxin (ETX) produces severe, and frequently fatal, neurologic disease in ruminant livestock. The disorder is of worldwide distribution and, although vaccination has reduced its prevalence, ETX still causes substantial economic loss in livestock enterprises. The toxin is produced in the intestine as a relatively inactive prototoxin, which is subsequently fully enzymatically activated to ETX. When changed conditions in the intestinal milieu, particularly starch overload, favor rapid proliferation of this clostridial bacterium, large amounts of ETX can be elaborated. When sufficient toxin is absorbed from the intestine into the systemic circulation and reaches the brain, two neurologic syndromes can develop from this enterotoxemia. If the brain is exposed to large amounts of ETX, the lesions are fundamentally vasculocentric. The neurotoxin binds to microvascular endothelial receptors and other brain cells, the resulting damage causing increased vascular permeability and extravasation of plasma protein and abundant fluid into the brain parenchyma. While plasma protein, particularly albumin, pools largely perivascularly, the vasogenic edema becomes widely distributed in the brain, leading to a marked rise in intracranial pressure, coma, sometimes cerebellar herniation, and, eventually, often death. When smaller quantities of ETX are absorbed into the bloodstream, or livestock are partially immune, a more protracted clinical course ensues. The resulting brain injury is characterized by bilaterally symmetrical necrotic foci in certain selectively vulnerable neuroanatomic sites, termed focal symmetrical encephalomalacia. ETX has also been internationally listed as a potential bioterrorism agent. Although there are no confirmed human cases of ETX intoxication, the relatively wide species susceptibility to this toxin and its high toxicity mean it is likely that human populations would also be vulnerable to its neurotoxic actions. While the pathogenesis of ETX toxicity in the brain is incompletely understood, the putative mechanisms involved in neural lesion development are discussed.

Infection Dynamics of Clostridium perfringens Fingerprinting in Buffalo and Cattle of Punjab Province, Pakistan

Clostridium perfringens produces core virulence factors that are responsible for causing hemorrhagic abomasitis and enterotoxemia making food, animals, and humans susceptible to its infection. In this study, C. perfringens was isolated from necropsied intestinal content of buffalo and cattle belonging to four major bovine-producing regions in the Punjab Province of Pakistan for the purpose offind out the genetic variation. Out of total 160 bovine samples (n: 160), thirty-three (n: 33) isolates of C. perfringens were obtained from buffalo (Bubales bubalis) and cattle (Bos indicus) that were further subjected to biochemical tests; 16S rRNA based identification and toxinotyping was done using PCR (Polymerase Chain Reaction) and PFGE (Pulse Field Gel Electrophoresis) pulsotypesfor genetic diversity. Occurrence of C. perfringens was found to be maximum in zone-IV (Bhakkar and Dera Ghazi Khan) according to the heatmap. Correlation was found to be significant and positive among the toxinotypes (α-toxin, and ε-toxin). Response surface methodology (RSM) via central composite design (CCD) and Box-Behnken design (BBD) demonstrated substantial frequency of C. perfringens based toxinotypes in all sampling zones. PFGE distinguished all isolates into 26 different pulsotypes using SmaI subtyping. Co-clustering analysis based on PFGE further decoded a diversegenetic relationship among the collected isolates. This study could help us to advance toward disease array of C. perfringens and its probable transmission and control. This study demonstrates PFGE patterns from Pakistan, and typing of C. perfringens by PFGE helps illustrate and mitigate the incidence of running pulsotypes.

Clostridium perfringens-Induced Necrotic Diseases: An Overview

Clostridium perfringens, a prevalent Gram-positive bacterium, causes necrotic diseases associated with abundant life loss and economic burdens of billions of USD. The mechanism of C. perfringens-induced necrotic diseases remains largely unknown, in part, because of the lack of effective animal models and the presence of a large array of exotoxins and diverse disease manifestations from the skin and deep tissues to the gastrointestinal tract. In the light of the advancement of medical and veterinary research, a large body of knowledge is accumulating on the factors influencing C. perfringens-induced necrotic disease onset, development, and outcomes. Here, we present an overview of the key virulence factors of C. perfringens exotoxins. Subsequently, we focus on comprehensively reviewing C. perfringens-induced necrotic diseases such as myonecrosis, acute watery diarrhea, enteritis necroticans, preterm infant necrotizing enterocolitis, and chicken necrotic enteritis. We then review the current understanding on the mechanisms of myonecrosis and enteritis in relation to the immune system and intestinal microbiome. Based on these discussions, we then review current preventions and treatments of the necrotic diseases and propose potential new intervention options. The purpose of this review is to provide an updated and comprehensive knowledge on the role of the host–microbe interaction to develop new interventions against C. perfringens-induced necrotic diseases.

Navarro M, Li J, Shrestha A, Uzal F, A. McClane B. Pathogenicity and virulence of Clostridium perfringens

Clostridium perfringens is an extremely versatile pathogen of humans and livestock, causing wound infections like gas gangrene (clostridial myonecrosis), enteritis/enterocolitis (including one of the most common human food-borne illnesses), and enterotoxemia (where toxins produced in the intestine are absorbed and damage distant organs such as the brain). The virulence of this Gram-positive, spore-forming, anaerobe is largely attributable to its copious toxin production; the diverse actions and roles in infection of these toxins are now becoming established. Most C. perfringens toxin genes are encoded on conjugative plasmids, including the pCW3-like and the recently discovered pCP13-like plasmid families. Production of C. perfringens toxins is highly regulated via processes involving two-component regulatory systems, quorum sensing and/or sporulation-related alternative sigma factors. Non-toxin factors, such as degradative enzymes like sialidases, are also now being implicated in the pathogenicity of this bacterium. These factors can promote toxin action in vitro and, perhaps in vivo, and also enhance C. perfringens intestinal colonization, e.g. NanI sialidase increases C. perfringens adherence to intestinal tissue and generates nutrients for its growth, at least in vitro. The possible virulence contributions of many other factors, such as adhesins, the capsule and biofilms, largely await future study.

Bacteriological and molecular typing of Clostridium perfringens strains isolated in retail beef in Beijing, China

Clostridium perfringens is an important zoonotic pathogen. This study was designed to explore the prevalence and toxin types of C. perfringens in retail beef collected from Beijing, China. Among 221 beef samples collected, 53 samples were positive for C. perfringens, resulting in the average prevalence as 23.98%. By toxin gene-based typing, the most C. perfringens strains belong to type A (96.23%, 51/53), only 2 strains were identified as type D. By a multi-locus sequence typing (MLST)-based analysis, a total of 36 sequence types (STs) were detected, and the most STs (n=30) represented just a single strain. These finding suggested that the prevalence of C. perfringens in retail beef in Beijing was considerably high and these bacteria displayed extreme diversity in genetics.

Cattle and goats' humoral response to vaccination with Clostridium perfringens type D purified epsilon toxoids

Herd vaccination is an important preventive measure against enterotoxemia in ruminants. Vaccination in goats should be performed every four months, and recent studies have shown that immunity in cattle lasts for less than one year. One of the mechanisms for increasing the duration of the immune response is to use purified toxoids as immunogens. The aim of the present study was to evaluate the humoral response in cattle and goats after vaccination with purified and semi-purified Clostridium perfringens type D epsilon toxoid. The following three different vaccines were used: vaccine 1 (V1), a semi-purified toxoid adsorbed to aluminum hydroxide; vaccine 2 (V2), a purified toxoid adsorbed to aluminum hydroxide; and vaccine (V3), a purified toxoid adsorbed on chitosan microparticles. Groups of cattle (n = 6-7) and goats (n = 6-7) were vaccinated on days 0 and 30, and serum samples for antitoxin titration were collected every 30 days for one-year post-vaccination. Goats were revaccinated on day 360, and their serum was evaluated on days 367 and 374. The antibody peaks ranged between 6.90 and 11.47 IU/mL in cattle and from 1.11 to 4.40 IU/mL in goats. In cattle administered with the V1 and V2 vaccines, we observed that the antibody titers were maintained above 0.2 IU/mL until the end of the experiment. In goats, V2 elicited long-lasting antibodies, and all animals maintained the protective titers for 210 days after the first dose. In conclusion, the purified toxoid vaccine with aluminum hydroxide adjuvant was able to induce strong and long-lasting humoral responses in both species and could be an alternative for improving the immunization schedule against enterotoxemia in goats and cattle.

Comparative Genomics of Clostridium perfringens Reveals Patterns of Host-Associated Phylogenetic Clades and Virulence Factors

Clostridium perfringens is an opportunistic pathogenic bacterium that infects both animals and humans. Clostridium perfringens genomes encode a diverse array of toxins and virulence proteins, which continues to expand as more genomes are sequenced. In this study, the genomes of 44 C. perfringens strains isolated from intestinal sections of diseased cattle and from broiler chickens from diseased and healthy flocks were sequenced. These newly assembled genomes were compared to 141 publicly available C. perfringens genome assemblies, by aligning known toxin and virulence protein sequences in the assemblies using BLASTp. The genes for alpha toxin, collagenase, a sialidase (nanH), and alpha-clostripain were present in at least 99% of assemblies analyzed. In contrast, beta toxin, epsilon toxin, iota toxin, and binary enterotoxin of toxinotypes B, C, D, and E were present in less than 5% of assemblies analyzed. Additional sequence variants of beta2 toxin were detected, some of which were missing the leader or signal peptide sequences and therefore likely not secreted. Some pore-forming toxins involved in intestinal diseases were host-associated, the netB gene was only found in avian isolates, while netE, netF, and netG were only present in canine and equine isolates. Alveolysin was positively associated with canine and equine strains and only present in a single monophyletic clade. Strains from ruminant were not associated with known virulence factors and, except for the food poisoning associated clade, were present across the phylogenetic diversity identified to date for C. perfringens. Many C. perfringens strains associated with food poisoning lacked the genes for hyaluronidases and sialidases, important for attaching to and digesting complex carbohydrates found in animal tissues. Overall, the diversity of virulence factors in C. perfringens makes these species capable of causing disease in a wide variety of hosts and niches.

ANTIBODY RESPONSE TO EPSILON TOXIN OF CLOSTRIDIUM PERFRINGENS IN CAPTIVE ADULT SPRINGBOK (ANTIDORCAS MARSUPIALIS), IMPALA (AEPYCEROS MELAMPUS), ALPACA (VICUGNA PACOS), AND RED-NECKED WALLABY (MACROPUS RUFOGRISEUS) OVER A YEAR

Enterotoxemia is an important issue in various zoological taxa. In this study, serologic responses over a 1-yr period after vaccination with a multivalent clostridial vaccine were evaluated in 10 adult springboks (Antidorcas marsupialis), 12 impalas (Aepyceros melampus), seven alpacas (Vicugna pacos), and five red-necked wallabies (Macropus rufogriseus). Antibody production to the Clostridium perfringens type D epsilon toxin component of the vaccine was measured using an indirect enzyme-linked immunosorbent assay and determined as the percentage of inhibition (% inhib). Initial % inhib was (0.01-18.9)%. All animals received initial vaccination with a booster vaccine 4 weeks apart. Serum samples were collected at T0 (nonvaccinated), 15, 30, 60, 180, and 360 days postvaccination (dpv) for analysis. The vaccine induced a high antibody response that peaked at 15, 30, and 60 dpv in springboks, 30 and 60 dpv in impalas (P < 0.01), and 60 dpv in alpacas and wallabies (P < 0.01). The booster vaccine was followed by a high antibody response, which slowly decreased with time. The antibody response was significantly higher at 360 dpv than at T0 in wallabies and alpacas (P < 0.01). In impalas and springboks, it appeared that a booster every 6 mo might be required to maintain an antibody response above baseline (P < 0.01). Because no challenge studies were performed, it is unknown whether the measured humoral immune responses would have been protective. Further research is warranted to investigate protective effects of antibodies to inoculation challenge in nondomestic species.

Occurrence and Toxicogenetic Profiling of Clostridium perfringens in Buffalo and Cattle: An Update from Pakistan

Clostridium perfringens is a Gram-positive bacterium that possess seven toxinotypes (A, B, C, D, E, F, and G) that are responsible for the production of six major toxins, i.e., α, β, ε, ι, CPE, and NetB. The aim of this study is to find out the occurrence of toxinotypes in buffalo and cattle of Punjab province in Pakistan and their corresponding toxin-encoding genes from the isolated toxinotypes. To accomplish this aim, six districts in Punjab province were selected (i.e., Lahore, Sahiwal, Cheecha Watni, Bhakkar, Dera Ghazi Khan, and Bahawalpur) and a total of 240 buffalo and 240 cattle were selected for the collection of samples. From isolation and molecular analysis (16S rRNA), it was observed that out of seven toxinotypes (A–G), two toxinotypes (A and D) were found at most, whereas other toxinotypes, i.e., B, C, E, F, and G, were not found. The most frequently occurring toxinotype was type A (buffalo: 149/240; cattle: 157/240) whereas type D (buffalo: 8/240 cattle: 7/240) was found to occur the least. Genes encoding toxinotypes A and D were cpa and etx, respectively, whereas genes encoding other toxinotypes were not observed. The occurrence of isolated toxinotypes was studied using response surface methodology, which suggested a considerable occurrence of the isolated toxinotypes (A and D) in both buffalo and cattle. Association between type A and type D was found to be significant among the isolated toxinotypes in both buffalo and cattle (p ≤ 0.05). Correlation was also found to be positive and significant between type A and type D. C. perfringens exhibits a range of toxinotypes that can be diagnosed via genotyping, which is more reliable than classical toxinotyping.

Cardiopulmonary Lesions in Sheep Produced by Experimental Acute Clostridium Perfringens Type D Enterotoxemia

Enterotoxemia caused by Clostridium perfringens type D is one of the most prevalent clostridial diseases of sheep. The lesions of the acute form of this disease, particularly the cerebral lesions, are well characterized; however, detailed descriptions of the cardiac and pulmonary lesions are lacking. Here we describe cardiopulmonary lesions in experimental acute type D enterotoxemia in sheep and determine the role of epsilon toxin (ETX) in the development of these lesions. Four groups of 6 sheep were intraduodenally inoculated with either a wild-type C. perfringens type D strain; its etx knockout mutant, which is unable to produce ETX; the etx mutant complemented with the wild-type etx gene, which regains the ETX toxigenic ability; or sterile culture medium as a control. All sheep were subjected to postmortem examination within 24 hours of inoculation. Lesion scores were compared between groups for pulmonary edema; hydrothorax; ascites; hydropericardium; endocardial, myocardial and epicardial hemorrhages; microscopic lesions of acute myocardial degeneration and necrosis; and myocardial, endocardial, and epicardial edema, hemorrhage, and inflammation. Only sheep inoculated with the wild-type and complemented ETX-toxigenic bacterial strains developed cardiopulmonary lesions, which were present in varying degrees of severity and proportions. These lesions were not present in sheep inoculated with the etx mutant or in the negative control. We conclude that severe acute cardiopulmonary lesions in sheep with experimental enterotoxemia are associated with the capacity of the strains to produce ETX. These changes are likely contributors to the clinical signs and even death of affected animals.

Genomic Analysis of Clostridium perfringens BEC/CPILE-Positive, Toxinotype D and E Strains Isolated from Healthy Children

Clostridium perfringens toxinotype D, toxinotype E, and gastroenteritis-linked BEC/CPILE-positive strains have never been reported in healthy children. We isolated, whole-genome sequenced and bioinformatically characterised three C. perfringens isolates-type D (IQ1), type E (IQ2) and BEC/CPILE-positive (IQ3), recovered from the stools of three healthy two-year-olds, which were further compared to 128 C. perfringens genomes available from NCBI. The analysis uncovered a previously under-described putative toxin gene alv (alveolysin) encoded by isolates IQ2 and IQ3, which appeared to be a clade-specific trait associated with strains from domestic animals. A plasmid analysis indicated that the iota-toxin was encoded on a near-intact previously described plasmid pCPPB-1 in type E strain IQ2. The BEC genes becA and becB were carried on a near-identical pCPOS-1 plasmid previously associated with Japanese gastroenteritis outbreaks. Furthermore, a close phylogenetic relatedness was inferred between the French C. perfringens type E isolates cp515.17 and newly sequenced IQ2, suggesting geographical links. This study describes novel C. perfringens isolates from healthy individuals which encode important toxin genes, indicating the potential spread of these veterinary and clinically important strains and mobile genetic elements, and highlights areas for future research.

Clostridial diseases diagnosed in cattle from the South of Rio Grande do Sul, Brazil. A forty-year survey (1978-2018) and a brief review of the literature

ABSTRACT: Clostridial diseases are important causes of livestock losses in the southern Rio Grande do Sul. Since 1978 annual surveys conducted at the “Laboratório Regional de Diagnóstico” of the “Universidade Federal de Pelotas” (LRD-UFPel) have shown that clostridial diseases represent 10.40% of the bacterial diseases diagnosed in cattle and 1.65% of all diseases diagnosis in cattle over a 40-year period. The purpose of this study is to review the clinical, epidemiological and pathological aspects of the clostridial diseases diagnosed in cattle from January 1978 to December 2018 at the LRD-UFPel in the hopes that it will constitute a useful guide for field veterinary practitioners and interested farmers. We assessed and review the necropsy protocols of 6,736 cattle; these necropsies were performed either by LRD-UFPel faculty or by field veterinary practitioners; 111 outbreaks (1.65%) were diagnosed as clostridial disease, distributed as follows: 35 outbreaks of tetanus, 34 of blackleg, 23 of bacillary hemoglobinuria, 11 of malignant edema (gas gangrene), and eight of botulism. Approximately 904, from a total of 42,480 cattle at risk, died in these outbreaks.

Mechanisms of Action and Cell Death Associated with Clostridium perfringens Toxins

Clostridium perfringens uses its large arsenal of protein toxins to produce histotoxic, neurologic and intestinal infections in humans and animals. The major toxins involved in diseases are alpha (CPA), beta (CPB), epsilon (ETX), iota (ITX), enterotoxin (CPE), and necrotic B-like (NetB) toxins. CPA is the main virulence factor involved in gas gangrene in humans, whereas its role in animal diseases is limited and controversial. CPB is responsible for necrotizing enteritis and enterotoxemia, mostly in neonatal individuals of many animal species, including humans. ETX is the main toxin involved in enterotoxemia of sheep and goats. ITX has been implicated in cases of enteritis in rabbits and other animal species; however, its specific role in causing disease has not been proved. CPE is responsible for human food-poisoning and non-foodborne C. perfringens-mediated diarrhea. NetB is the cause of necrotic enteritis in chickens. In most cases, host–toxin interaction starts on the plasma membrane of target cells via specific receptors, resulting in the activation of intracellular pathways with a variety of effects, commonly including cell death. In general, the molecular mechanisms of cell death associated with C. perfringens toxins involve features of apoptosis, necrosis and/or necroptosis.

Histopathological study of encephalomalacia in neonatal calves and application of neuronal and axonal degeneration marker

Five calves that had shown neurological symptoms within 9 days after birth were histopathologically diagnosed as encephalomalacia. Two calves showed bilateral laminar cerebrocortical necrosis and neuronal necrosis in the corpus striatum and hippocampus. Since the distributional pattern of the lesions was consistent with that of global ischemia in other species, the lesions were probably hypoxic/ischemic encephalopathy consistent with the history of dystocia and perinatal asphyxia. One calf also showed bilateral laminar cerebrocortical necrosis. However, the lesions were chronic ones, because the calf had survived for long time and necropsied at postnatal day 118. Additionally, the lesions did not involve the corpus striatum and hippocampus. The other two calves showed multifocal necrosis with vascular lesions characterized by fibrin thrombi, perivascular edema and perivascular hyaline droplets in the cerebral cortex, corpus striatum, thalamus, brain stem and cerebellum. Considering the age of onsets and histopathological appearance, it was possible that latter three calves were also hypoxic/ischemic encephalopathy, however, exact cause of them was not revealed. In all calves, degenerated/necrotic neurons showed positive reactions for Fluoro-Jade C and degenerated axons showed immunoreactivity for Alzheimer precursor protein A4. Therefore, these markers were applicable to examination of brain injury in neonatal calves.

Rethinking the role of alpha toxin in Clostridium perfringens-associated enteric diseases: a review on bovine necro-haemorrhagic enteritis

Bovine necro-haemorrhagic enteritis is an economically important disease caused by Clostridium perfringens type A strains. The disease mainly affects calves under intensive rearing conditions and is characterized by sudden death associated with small intestinal haemorrhage, necrosis and mucosal neutrophil infiltration. The common assumption that, when causing intestinal disease, C. perfringens relies upon specific, plasmid-encoded toxins, was recently challenged by the finding that alpha toxin, which is produced by all C. perfringens strains, is essential for necro-haemorrhagic enteritis. In addition to alpha toxin, other C. perfringens toxins and/or enzymes might contribute to the pathogenesis of necro-haemorrhagic enteritis. These additional virulence factors might contribute to breakdown of the protective mucus layer during initial stage of pathogenesis, after which alpha toxin, either or not in synergy with other toxins such as perfringolysin O, can act on the mucosal tissue. Furthermore, alpha toxin alone does not cause intestinal necrosis, indicating that other virulence factors might be needed to cause the extensive tissue necrosis observed in necro-haemorrhagic enteritis. This review summarizes recent research that has increased our understanding of the pathogenesis of bovine necro-haemorrhagic enteritis and provides information that is indispensable for the development of novel control strategies, including vaccines.

Non-toxic perfringolysin O and α-toxin derivatives as potential vaccine candidates against bovine necrohaemorrhagic enteritis

Bovine necrohaemorrhagic enteritis is a fatal Clostridium perfringens type A-induced disease that is characterised by sudden death. Recently the involvement of perfringolysin O and α-toxin in the development of necrohaemorrhagic lesions in the gut of calves was suggested, and thus derivatives of these toxins are potentially suitable as vaccine antigens. In the current study, the perfringolysin O derivative PFO^L491D, alone or in combination with α-toxin derivative GST-cpa_247-370, was evaluated as possible vaccine candidate, using in vitro assays. PFO^L491D showed no haemolytic effect on horse red blood cells and no cytotoxic effect on bovine endothelial cells. Furthermore, calves immunised with PFO^L491D raised antibodies against perfringolysin O that could inhibit the perfringolysin O-associated haemolytic activity on horse red blood cells. Antisera from calves immunised with PFO^L491D had a significantly higher neutralising capacity against the cytotoxic effect of C. perfringens culture supernatant to bovine endothelial cells than serum from control calves (P <0.05). Immunisation of calves with PFO^L491D in combination with GST-cpa_247-370 elicited antibodies against perfringolysin O and α-toxin and consequently inhibited both the perfringolysin O-associated haemolytic activity and the α-toxin-associated lecithinase activity in vitro. Additionally, the neutralising ability of these antisera on the cytotoxic effect of C. perfringens culture supernatant to bovine endothelial cells was significantly higher than that from calves immunised with PFO^L491D (P <0.001). In conclusion, perfringolysin O derivative PFO^L491D is an immunogenic antigen that can potentially be used to produce vaccine against bovine necrohaemorrhagic enteritis. Including α-toxin derivative GST-cpa_247-370 has an additional protective effect and therefore vaccination of calves with a combination of both antigens seems even more promising.

Clostridium perfringens type-D enterotoxaemia in cattle: the diagnostic significance of intestinal epsilon toxin

The aims of this study were to describe 42 cases of Clostridium perfringens type-D enterotoxaemia in cattle seen between 2003 and 2014 and to determine the diagnostic value of detecting epsilon toxin in bovine intestinal content. All cases in the series had histological brain changes considered pathognomonic for C. perfringens type-D enterotoxaemia in sheep and goats and the epsilon toxin of C. perfringens was concurrently detected in the intestinal contents of 15 (36 per cent) cases. The data from the case series indicate that intestinal epsilon toxin has a sensitivity of 56 per cent compared with histology of the brain for diagnosis of bovine C. perfringens type-D enterotoxaemia. The diagnostic specificity of detecting epsilon toxin in bovine intestinal content was investigated by screening intestinal contents of 60 bovine carcases submitted for postmortem examination. Epsilon toxin was detected in 11 (18 per cent) carcases but no pathognomonic histological brain change was found in any. The specificity of intestinal epsilon toxin was estimated to be 80.4 per cent. These studies demonstrate that for a definitive diagnosis of C. perfringens type-D enterotoxaemia in cattle histological examination of the brain is essential as the presence of epsilon toxin in the intestinal contents alone is neither sensitive nor specific enough.

Animal models to study the pathogenesis of human and animal Clostridium perfringens infections

The most common animal models used to study Clostridium perfringens infections in humans and animals are reviewed here. The classical C. perfringens-mediated histotoxic disease of humans is clostridial myonecrosis or gas gangrene and the use of a mouse myonecrosis model coupled with genetic studies has contributed greatly to our understanding of disease pathogenesis. Similarly, the use of a chicken model has enhanced our understanding of type A-mediated necrotic enteritis in poultry and has led to the identification of NetB as the primary toxin involved in disease. C. perfringens type A food poisoning is a highly prevalent bacterial illness in the USA and elsewhere. Rabbits and mice are the species most commonly used to study the action of enterotoxin, the causative toxin. Other animal models used to study the effect of this toxin are rats, non-human primates, sheep and cattle. In rabbits and mice, CPE produces severe necrosis of the small intestinal epithelium along with fluid accumulation. C. perfringens type D infection has been studied by inoculating epsilon toxin (ETX) intravenously into mice, rats, sheep, goats and cattle, and by intraduodenal inoculation of whole cultures of this microorganism in mice, sheep, goats and cattle. Molecular Koch's postulates have been fulfilled for enterotoxigenic C. perfringens type A in rabbits and mice, for C. perfringens type A necrotic enteritis and gas gangrene in chickens and mice, respectively, for C. perfringens type C in mice, rabbits and goats, and for C. perfringens type D in mice, sheep and goats.

The synergistic necrohemorrhagic action of Clostridium perfringens perfringolysin and alpha toxin in the bovine intestine and against bovine endothelial cells

Bovine necrohemorrhagic enteritis is a major cause of mortality in veal calves. Clostridium perfringens is considered as the causative agent, but there has been controversy on the toxins responsible for the disease. Recently, it has been demonstrated that a variety of C. perfringens type A strains can induce necrohemorrhagic lesions in a calf intestinal loop assay. These results put forward alpha toxin and perfringolysin as potential causative toxins, since both are produced by all C. perfringens type A strains. The importance of perfringolysin in the pathogenesis of bovine necrohemorrhagic enteritis has not been studied before. Therefore, the objective of the current study was to evaluate the role of perfringolysin in the development of necrohemorrhagic enteritis lesions in calves and its synergism with alpha toxin. A perfringolysin-deficient mutant, an alpha toxin-deficient mutant and a perfringolysin alpha toxin double mutant were less able to induce necrosis in a calf intestinal loop assay as compared to the wild-type strain. Only complementation with both toxins could restore the activity to that of the wild-type. In addition, perfringolysin and alpha toxin had a synergistic cytotoxic effect on bovine endothelial cells. This endothelial cell damage potentially explains why capillary hemorrhages are an initial step in the development of bovine necrohemorrhagic enteritis. Taken together, our results show that perfringolysin acts synergistically with alpha toxin in the development of necrohemorrhagic enteritis in a calf intestinal loop model and we hypothesize that both toxins act by targeting the endothelial cells.

Brain lesions associated with clostridium perfringens type D epsilon toxin in a Holstein heifer calf

A 6-month-old dairy heifer calf with no premonitory signs was acutely down after the morning feeding and could not rise. On presentation, the heifer was in right lateral recumbency and moribund with opisthotonus and left hind limb paddling. Following euthanasia, gross examination of the brain revealed multifocal loss of gray-white matter distinction and extensive petechiae throughout the brainstem. On histopathological examination, there was striking white matter edema and marked perivascular proteinaceous edema surrounding many arterioles and venules (microangiopathy), mainly in the white matter of the internal capsule, thalamus, midbrain, cerebellum, and cerebellar peduncles. The perivascular neuropil was strongly positive for Alzheimer precursor protein A4. Clostridium perfringens epsilon toxin was detected in the intestinal contents. This is the first report of microangiopathy in postneonatal cattle associated with the detection of epsilon toxin in the intestinal contents.

Effects of Clostridium perfringens alpha and epsilon toxins in the bovine gut

Clostridium perfringens alpha and epsilon toxins produce enterotoxaemia in sheep and goats. However, the information regarding the pathophysiology of alpha and epsilon toxins in the bovine intestine is still scanty. In this study, intestinal loops were performed in the ileum and colon of three one-week-old Holstein and two four-week-old crossbreed calves. Laparotomy was performed in all calves under anaesthesia and four loops -three cm long- were performed in the small and large intestines. For both intestines, loops were inoculated with alpha or epsilon toxins. Tissue samples from all loops were obtained and processed for routine histology and for transmission electron microscopy. Congestion was observed in toxin treated loops. Fluid accumulation in the gut lumen was prominent in all treated loops, but in epsilon treated ones the mucous was also haemorrhagic. The histology revealed large amount of exfoliated epithelial cells in the lumen of alpha toxin treated loops and severe haemorrhage was observed in the lamina propria of epsilon toxin treated colonic loops. Despite some necrotic exfoliated enterocytes, no ultraestructural changes were observed in alpha toxin treated loops, though with epsilon toxin the loops exhibited dilation of the intercellular space in the mucosa of both, small and large intestines. These observations indicate that both, alpha and epsilon toxins can alter the intestinal barrier, in calves and are pathogenic for this species.

Focal Symmetrical Encephalomalacia in a Goat

Focal symmetrical encephalomalacia (FSE) is the most prominent lesion seen in the chronic form of enterotoxemia caused by Clostridium perfringens type D in sheep. However, this lesion has not been reported in goats. The current paper reports a case of FSE in a goat from the state of Paraíba in the Brazilian semiarid region. As reported by the farmer, 30, 4–48-month-old animals from a flock of 150 goats died after showing nervous signs, including blindness and recumbence, for periods varying between 1 and 14 days. The flock was grazing native pasture supplemented with wheat and corn bran. Additionally, lactating goats were supplemented with soybeans. A 4-month-old goat with nervous signs was examined clinically and then necropsied 3 days after the onset of clinical signs. Bilateral, focal, and symmetrical areas of brown discoloration were observed in the internal capsule and thalamus. Histologic lesions in these areas consisted of multifocal, bilateral malacia with a few neutrophils; endothelial cell swelling; perivascular edema; and hemorrhages. The etiology of these lesions was not determined. However, FSE is considered pathognomonic for C. perfringens type D enterotoxemia in sheep, and it is speculated that this microorganism was the etiologic agent in the present case. The flock had been vaccinated against type D enterotoxemia only once, approximately 3 months before the beginning of the outbreak. Insufficient immunity due to the incorrect vaccination protocol, low efficacy of the vaccine used, and a diet including large amounts of highly fermentable carbohydrates were suspected to be predisposing factors for this outbreak.

Focal symmetrical encephalomalacia in sheep

Focal symmetrical encephalomalacia (FSE) is the most prominent lesion seen in the chronic form of enterotoxemia by Clostridium perfringens type D. This paper reports FSE in sheep in Brazil. Six deaths occurred within a seven days period in a flock of 70, four to 30-month-old Santa Inês sheep in the state of Paraíba in the Brazilian semiarid. The flock was grazing a paddock of irrigated sprouting Cynodon dactylon (Tifton grass), and supplemented, ad libitum, with a concentrate of soybean, corn and wheat. Nervous signs included blindness and recumbence. A 19 month-old sheep was examined clinically and necropsied after a clinical course of three days. Gross lesions were herniation of the cerebellar vermis and multifocal, bilateral, symmetric brownish areas in the internal capsule, thalamus and cerebellar peduncles. Histologic lesions were multifocal, bilateral malacia with some neutrophils, swelling of blood vessels endothelium, perivascular edema, and hemorrhages. The flock was vaccinated, before the outbreak, with only one dose of Clostridium perfringens type D vaccine. Two factors are suggested to be important for the occurrence of the disease: insufficient immunity due to the incorrect vaccination; and high nutritional levels by the supplementation with highly fermentable carbohydrates.