Avian colibacillosis caused by an intestinal pathogenic Escherichia coli isolate from calf diarrhea

An intestinal pathogenic Escherichia coli isolate from calf diarrhea, containing the iutA, f17A, afa-8D, and cnf2 genes, was able to cause avian colibacillosis after experimental infection in chickens. Intra-tracheal inoculation and spray of this strain caused 10% of mortality and gross lesions, including airsacculitis, pericarditis, and perihepatitis. These results suggest that some bovine pathogenic E. coli can cause extra-intestinal infections in other animal species.     

Serological and molecular comparison of Mannheimia haemolytica and Pasteurella trehalosi strains isolated from wild and domestic ruminants in the French Alps

Over a period of 17 years, 84 bacterial isolates identified as Mannheimia haemolytica or M. glucosida, and 52 isolates identified as Pasteurella trehalosi were detected in the lungs of domestic and wild ruminants in the French Alps. The isolates were serotyped according to their surface capsular antigens, and those sharing common antigens were further characterized by pulsed field gel electrophoresis. The results showed that the bacterial isolates included in the study clustered according to the host species from which they were isolated. These findings indicate that the transmission of serotypes of M. haemolytica, M. glucosida or P. trehalosi from an animal host in which they are common to another species sharing the same geographical space may be a rare epidemiological event.     

Mannheimia haemolytica serotype A1 exhibits differential pathogenicity in two related species, Ovis canadensis and Ovis aries

Mannheimia haemolytica causes pneumonia in both bighorn sheep (BHS, Ovis canadensis) and domestic sheep (DS, Ovis aries). Under experimental conditions, co-pasturing of BHS and DS results in fatal pneumonia in BHS. It is conceivable that certain serotypes of M. haemolytica carried by DS are non-pathogenic to them, but lethal for BHS. M. haemolytica serotypes A1 and A2 are carried by DS in the nasopharynx. However, it is the serotype A2 that predominantly causes pneumonia in DS. The objectives of this study were to determine whether serotype A1 exhibits differential pathogenicity to BHS and DS, and to determine whether leukotoxin (Lkt) secreted by this organism is its primary virulence factor. Three groups each of BHS and DS were intra-tracheally administered either 1 x 10(9)cfu of serotype A1 wild-type (lktA-Wt group), Lkt-deletion mutant of serotype A1-(lktA-Mt group), or saline (control group), respectively. In the lktA-Wt groups, all four BHS died within 48h while none of the DS died during the 2-week study period. In the lktA-Mt groups, none of the BHS or DS died. In the control groups, one DS died due to an unrelated cause. Necropsy and histopathological findings revealed that death of BHS in the lktA-Wt group was due to bilateral, fibrinohemorrhagic pneumonia. Although the A1-Mt-inoculated BHS were clinically normal, on necropsy, lungs of two BHS showed varying degrees of mild chronic pneumonia. These results indicate that M. haemolytica serotype A1 is non-pathogenic to DS, but highly lethal to BHS, and that Lkt is the primary virulence factor of M. haemolytica.     

一起犊牛脑膜炎的临床处置与分析思考

在犊牛初生疾病的诊治上,犊牛脑膜炎往往与犊牛低血糖症、弱犊症伴随发生,在临床诊断不确定、诊疗处置随意化的影响下,极易造成误诊误治,引起诊疗失败。为切实加强犊牛脑膜炎的诊治,本文就一起犊牛脑膜炎的临床诊治过程进行分析,并就发病机理、诊断思路和防控进行讨论,提出了相应的思考与见解,从根本上拓宽犊牛初生疾病诊断视野,提高犊牛疾病诊治成功率提供一定的参考借鉴。     

Cytotoxicity and cytokine production by bovine alveolar macrophages challenged with wild type and leukotoxin-deficient Mannheimia haemolytica

The aim of this study was to investigate the use of ultrasound (US) guidance to perform sciatic and saphenous nerve blocks in dogs. Five dogs were sedated with medetomidine and butorphanol. A high-resolution US transducer was used to locate the nerves, guide placement of the needle and visualise the perineural injection of lidocaine 2%. Electrostimulation was used to confirm correct placement prior to the sciatic block. Nerve functions were evaluated over a 3 h period following administration of atipamezole. Successful identification of the nerves and the quality of the blocks were recorded. Location of the nerves, complete sensory block of the saphenous nerve, and partial to complete sensory and motor blocks of the sciatic nerve were achieved in all dogs. The resultant US guidance is potentially valuable for blocking the sciatic and saphenous nerves in dogs, although further work will be required to ensure a complete block of the sciatic nerve.     

Immunohistochemical detection of <Emphasis Type="Italic">Mannheimia (Pasteurella) haemolytica</Emphasis> antigens in goats with natural pneumonia

Pneumonia is a leading cause of loss to ruminants throughout the world. Mannheimia (Pasteurella) haemolytica is one of the most important etiological agent of pneumonia in cattle, sheep, and goats. This study was carried out to determine the incidence of M.haemolytica antigens using immunohistochemistry labelling of formalin-fixed, paraffin-embedded tissues in pneumonic lungs of goats slaughtered at abattoir, and then to compare these immunohistochemistry results with the results of bacterial isolation. For these objectives, a total of 1505 goat lungs slaughtered in slaughterhouse were grossly examined and pneumonia was detected in 74 cases (4.91%). Of these, with the exception of verminous pneumonia observed in 32 cases, on 42 pneumonic lungs immunohistochemical examinations were performed. Formalin-fixed and paraffin-embedded lung tissue samples were immunohistochemically stained by the avidin-biotin-peroxidase complex (ABC) procedure using polyclonal antibodies to detect M.haemolytica antigens. Pneumonic lesions were more frequently encountered in cranioventral lobes than caudal lobes, and characterized by irregular lobular foci of atelectasis or lobar pneumonia. The presence of M.haemolytica antigens was detected in 19 (45%) out of 42 pneumonic lungs. Bacterial antigens were found most frequently in the cytoplasm of bronchial and bronchiolar epithelial cells, in the swirling degenerating leukocytes in the alveoli, and in the degenerating leukocytes in the area of coagulation necrosis, less frequently in the epithelial cells of bronchial glands, and lymphoid cells. Conclusionly, immunohistochemical detection of M.haemolytica antigens in pneumonic lungs appear to be more reliable compared to bacterial isolation.     

Diversity of Mannheimia haemolytica and Pasteurella trehalosi Serotypes from Apparently Healthy Sheep and Abattoir Specimens in the Highlands of Wollo,North East Ethiopia

The prevalence and serotypic diversity of Mannheimia [Pasteurella] haemolytica and Pasteurella trehalosi from nasal swabs, sera and abattoir specimens from sheep in the highlands of Wollo, North East Ethiopia was investigated. Prevalence rates of 83% and 75% of these microorganisms were found in the serum samples and nasal swabs, respectively, from apparently healthy sheep. In a local abattoir, 205 lungs were investigated, 34% of which showed pneumonia, from which samples were collected from 51 lungs and the same number of corresponding tonsils. Mannheimia and Pasteurella species were isolated from 59% of these pneumonic lungs and 69% of the respective tonsils. M. haemolytica serotypes accounted for 41 (59%) and P. trehalosi for 11 (32%) of the isolates from the abattoir specimens. The majority (67%) of isolates from nasal swabs were P. trehalosi, M. haemolytica being isolated f rom 4 (13%) of the swabs. M. glucosida was isolated only from the tonsils. The predominant serotypes of the isolates from both the nasal swabs and the abattoir specimens were M. haemolytica A1 (17%) and P. trehalosi T4 (16%) and T3 (13%). P. trehalosi T15 was less commonly encountered, while M. haemolytica A9 and A13 were not isolated. Studies on sera from 100 sheep indicated that antibodies against M. haemolytica serotype A1 (14%) were most common, followed by A5 and A8 (each 10%) and A9 and P. trehalosi T3 (each 9%) and T4 (8%). Antibodies against M. glucosida or serotype A11 occurred in 2% of the sera. Multiple serotypes were common in all types of samples. The importance of including in vaccines the most prevalent serotypes involved in the pneumonia of sheep in the area is discussed.     

Toxicity in goats caused by oleander (Nerium oleander)

Cases of poisoning by oleander (Nerium oleander) were observed in several species, except in goats. This study aimed to evaluate the pathological effects of oleander in goats. The experimental design used three goats per group: the control group, which did not receive oleander and the experimental group, which received leaves of oleander (50 mg/kg/day) for six consecutive days. On the seventh day, goats received 110 mg/kg of oleander leaves four times at one-hourly interval. A last dose of 330 mg/kg of oleander leaves was given subsequently. After the last dose was administered, clinical signs such as apathy, colic, vocalizations, hyperpnea, polyuria, and moderate rumen distention were observed. Electrocardiogram revealed second-degree atrioventricular block. Death occurred on an average at 92 min after the last dosing. Microscopic evaluation revealed renal necrosis at convoluted and collector tubules and slight myocardial degeneration was observed by unequal staining of cardiomyocytes. Data suggest that goats appear to respond to oleander poisoning in a manner similar to other species.     

Differential susceptibility to tetracycline,oxytetracycline and doxycycline of the calf pathogens Mannheimia haemolytica and Pasteurella multocida in three growth media

For clinical isolates of bovine Mannheimia haemolytica and Pasteurella multocida, this study reports minimum inhibitory concentration (MIC) differences for tetracycline, oxytetracycline and doxycycline between cation‐adjusted Mueller‐Hinton broth (CAMHB), foetal bovine serum (FBS) and Roswell Park Memorial Institute (RPMI) medium. MICs were determined according to CLSI standards and additionally using five overlapping sets of twofold dilutions. Matrix effect: (a) free drug MICs and minimum bactericidal concentrations (MBC) for all drugs were significantly higher in FBS than in CAMHB for both pathogens (p < 0.001); (b) MICs and MBCs were higher for CAMHB and FBS compared to RPMI for P. multocida only. Net growth rate for P. multocida in CAMHB was significantly slower than in FBS and higher than in RPMI, correlating to MIC and MBC ranking. Drug effect: doxycycline MICs and MBCs were significantly lower (p < 0.001) in both CAMHB and FBS than tetracycline and oxytetracycline for both pathogens. Only for M. haemolytica were oxytetracycline MIC and MBC significantly lower than tetracycline, precluding the use of tetracycline to predict oxytetracycline susceptibility in this species. Determining potencies of tetracyclines in a physiological medium, such as FBS, is proposed, when the objective is correlation with pharmacokinetic data for dosage determination.     

Prevalence and molecular characterization of bovine Cryptosporidium in Qazvin province, Iran

The aim of this study was to determine the prevalence, variability with host age, and the genotypes of species of Cryptosporidium in cattle from 15 dairy farms in Qazvin province, Iran. Fecal samples, collected from 272 cattle during May 2006 to December 2007, were characterized microscopically. Oocysts from 51 positive samples were analyzed using PCR assay of 18S SSU rRNA, restriction fragment length polymorphism (RFLP) and sequencing. We identified 72.6% of the positive samples as Cryptosporidium parvum, 17.7% as Cryptosporidium andersoni, 7.8% as Cryptosporidium bovis and 1.9% as a novel genotype of C. parvum possessing a single mutation on MboII restriction. An infection rate of 19.5% of C. parvum among 174 pre-weaned calves was significantly higher than the 3.1% among 98 post-weaned calves (P < 0.0006). This is the first report of C. bovis and the new subgenotype of C. parvum in Iranian cattle.     

PCR-based detection of blood parasites in cattle and adult Rhipicephalus appendiculatus ticks

To ascertain the infection rate for tick-borne pathogens in Zambia, an epidemiological survey of Theileria parva, Babesia bigemina and Anaplasma marginale in traditionally managed Sanga cattle was conducted using PCR. Of the 71 native Zambian cattle, 28 (39.4%) were positive for T. parva, 16 (22.5%) for B. bigemina and 34 (47.9%) for A. marginale. The mixed infection rate in cattle was 8.5% (6/71), 16.9% (12/71), 7.0% (5/71) and 2.8% (2/71) for T. parva/B. bigemina, T. parva/A. marginale, B. bigemina/A. marginale and T. parva/B. bigemina/A. marginale, respectively.To predict the risk for transmission of tick-borne pathogens from ticks to cattle, a total of 74 Rhipicephalus appendiculatus ticks were collected from a location where cattle had been found positive for T. parva. Of the ticks collected, 10 (13.5%) were found to be PCR-positive for T. parva. The results suggest that the infection rate for tick-borne pathogens was relatively high in Sanga cattle and that adult R. appendiculatus ticks were highly infected with T. parva.     

Endectocide activity of a new long-action formulation containing 2.25% ivermectin+1.25% abamectin in cattle

The present work aimed to evaluate the endectocide activity of a new injectable long-action formulation, containing ivermectin (IVM) and abamectin (ABA). In each one of the four experiments performed, the following groups were formed: group I: 2.25% IVM (450 microg/kg)+1.25% ABA (250 microg/kg), group II: 3.15% IVM (630 microg/kg) and group III: control. Eighteen bovine naturally infected by gastrointestinal nematoda were selected for anthelmintic evaluation and necropsied on posttreatment day (PTD) 14 to estimate the total parasitic burden. For the Rhipicephalus (Boophilus) microplus field trial, 30 bovine were selected by means of counts of semi-engorged R. (B.) microplus and the therapeutic and residual efficacy evaluated by tick counts on PTDs 1, 3, 7, 14, 21, 28, 35, 42, 49, 56, 63, 70, 77, 84 and 91. In the stall test, 15 calves were artificially infested with 5000 R. (B.) microplus (Mozzo strain) larvae three times a week and daily collections of all the engorged female ticks detached from each calf were performed until the PTD 80. Forty bovine naturally infected with Dermatobia hominis larvae were selected and the number of larvae was counted by visual and tactile inspection on PTDs 3, 7, 14, 28, 35, 49, 63, 77, 91 and 105. In this trial, a formulation containing 1% doramectin (200 microg/kg) was also used. IVM+ABA formulation and 3.15% IVM eliminated four of the eight species of nematode identified. The anthelmintic efficacy of the avermectins association against Haemonchus placei, Cooperia spatulata and C. punctata was 89.64%, 98.84% and 97.69%, while 3.15% IVM achieved 30.98%, 84.79% and 75.56%, respectively. The two formulations evaluated showed reduced acaricide action on the PTD 1 and 3, reaching high efficacy percentages from PTD 14 onward. The IVM+ABA showed efficacy above 95% in the period between PTDs 21 and 49. In the stall test, it observed no difference (P>0.05) between the two formulations regarding the R. (B.) microplus counts during the entire evaluation period. IVM+ABA reduced the number of ticks from the PTD 1 to 77 (P<0.05) and 3.15% IVM reduced (P<0.05) the tick number from PTD 4 up to PTD 80. The three endectocides showed no difference (P>0.05) regarding the number of D. hominis larvae and prevented this parasite reestablishment until PTD 105. These results indicate that the IVM+ABA association showed higher anthelmintic activity and similar efficacy against arthropods to the formulation containing 3.15% IVM.     

A Bayesian evaluation of four immunological assays for the diagnosis of clinical cryptosporidiosis in calves

A Bayesian approach was used to evaluate four immunological assays for the clinical diagnosis of cryptosporidiosis in calves: an immunofluorescence assay (IFA), two ELISA tests and an immunochromatographic (dipstick) assay. Faecal samples from 287 calves aged less than 6 weeks with clinical signs of gastrointestinal disease were examined for the presence of Cryptosporidium spp. The high prevalence (63%) of Cryptosporidium spp. indicated the relevance of this agent in the aetiology of diarrhoea in calves. All diagnostic assays were found to be relatively specific (IFA: 94.8%; Tetra ELISA: 95.9%; Techlab ELISA: 92.7%; dipstick assay: 91.5%) and sensitive (IFA: 97.4%; Tetra ELISA: 93.6%; Techlab ELISA: 95.4%; dipstick: 87.8%). Despite a lower sensitivity, the dipstick assay provided a practical alternative to laboratory diagnosis of clinical cryptosporidiosis in calves.     

Outbreak of bovine clinical mastitis caused by Mycoplasma bovis in a North Italian herd

This report describes an outbreak of Mycoplasma bovis mastitis affecting 45 cows in a herd of 122 dairy cattle in Northern Italy. Clinically, the outbreak was characterized by agalactia, multiple swollen and painless quarters, high milk somatic cell count and unresponsiveness to conventional antibiotic therapy. M. bovis was isolated from the milk samples of all the 32 affected cows tested and from the mammary tissue of three affected cows that underwent necropsy. No other pathogens were isolated from these samples. Lesions in two of the necropsied cows were characterized by mild chronic suppurative mastitis and galactophoritis. The other necropsied cow showed a chronic necrosuppurative and pyogranulamaous galactophoritis, a condition not previously associated with M. bovis. M. bovis was detected immunohistochemically in the lumen of the affected mammary ducts suggesting that ascending infection via the teat canal was the likely route of transmission. No other intralesional pathogens were demonstrated microscopically.     

Detection of Fusobacterium necrophorum and Dichelobacter nodosus in lame cattle on dairy farms in New Zealand

Lameness in the dairy industry in New Zealand causes a problem in lost production, animal welfare and associated costs. To understand what bacteria may be present on the hooves of lame dairy cattle in this grass-fed system, samples were scraped from lame dairy cows and examined for the presence of Fusobacterium necrophorum (F. necrophorum) and Dichelobacter nodosus (D. nodosus) using the polymerase chain reaction (PCR). The PCR primers were designed to detect the presence of the lktA gene, which encodes a leukotoxin unique to F. necrophorum, and the fimA gene of D. nodosus. A total of 148 hoof scrapings were collected by farm staff over the period September 2005 to May 2006. F. necrophorum was detected in 79/148 of the samples, while D. nodosus was detected in 7/148 of the samples. The frequent finding of F. necrophorum within dairy herds in New Zealand is noteworthy and the occasional finding of D. nodosus on some dairy cattle suggests a possible role in both ovine and bovine hoof pathology.     

Culling decisions of dairy farmers during a 3-year Salmonella control study

Salmonella enterica subsp. enterica-serotypes lead to periodically increased morbidity and mortality in cattle herds. The bacteria can also lead to serious infections in humans. Consequently, Denmark has started a surveillance and control programme in 2002. The programme focuses on Salmonella Dublin which is the most prevalent and most persistent serotype in the Danish cattle population. A field study in 10 dairy herds with persistent Salmonella infections was carried out over three years to gain experience with control procedures including risk assessment, targeted control actions and test-and-cull procedures. From autumn 2003 until end of 2006 quarterly milk quality control samples from all lactating cows and biannual blood samples from all young stock above the age of three months were tested using an indirect antibody ELISA. The most recent and previous test results were used to categorise all animals into risk groups. These risk groups and all individual ELISA-results were communicated to the farmers as colour-coded lists four to six times per year. Farmers were advised to manage the risk of Salmonella transmission from cattle with repeatedly high ELISA results (flagged as "red") or cows with at least one recent moderately high ELISA result (flagged as "yellow") on the lists. Risk management included, e.g. culling or separation of the cows at calving. We analysed culling decisions using two models. For heifers a hierarchical multivariable logistic model with herd as random effect evaluated if animals with red and yellow flags had higher probability of being slaughtered or sold before first calving than animals without any risk flags. For adult cows a semi-parametric proportional hazard survival model was used to test the effect of number of red and yellow flags on hazards of culling at different time points and interactions with prevalence in the herd while accounting for parity, stage of lactation, milk yield, somatic cell count and the hierarchical structure of the data with animals clustered at herd level. This study illustrates how investigation of culling decisions made by herd managers when they have access to test-status of individual animals and overall apparent prevalence during control of an infection can lead to useful new knowledge. Overall herd managers were more likely to cull cattle with increasing number of yellow and red flags than animals with no flags. However, cattle were more likely to be culled with yellow and red flags during times with low or medium high within-herd seroprevalence than at times with high seroprevalence. These results are valuable knowledge for modelling and planning of control strategies and for making recommendations to farmers about control options.     

Evaluation of a survey approach to estimating the prevalence of cattle carrying antimicrobial-resistant Escherichia coli

A random survey of farms in the Highlands and Islands of Scotland provides estimated of the prevalence of calves, finishers and cows carrying ampicillin, apramycin and/or nalidixic acid resistant Escherichia coli. While the survey provides information on the geographical variation in risk, the results are of limited value for interpreting causality.     

Molecular epidemiology of Cryptosporidium subtypes in cattle in England

Samples of Cryptosporidium spp., collected in a cross-sectional study of calves (median age 26 days) from 41 farms in Cheshire, UK, underwent molecular typing. The aim was to determine naturally occurring species/genotypes and to investigate transmission pathways within a local area. Of 60 positive samples, 54 were sequenced at an 18S rRNA locus and 51 were typed at a GP60 locus. C. parvum was identified in 50 samples, three cases were C. bovis and one was Cryptosporidium deer-like genotype. Six GP60 subgenotypes were identified. One subgenotype (IIaA15G2R1) was highly prevalent throughout the study area. A single subgenotype was identified on 20/22 farms. Two subgenotypes were found on 2/22 farms. The spatial scan statistic detected a cluster of subgenotype IIaA15G2R1 comprising seven farms. This suggests local transmission of the parasite between farms. As most of the isolates detected were the potentially zoonotic C. parvum allele IIa, intervention strategies should be considered to reduce the threat to public health. Biosecurity measures may reduce transmission between farms and result in lower levels of environmental contamination.     

Chlamydiaceae in cattle: commensals, trigger organisms, or pathogens?

Epidemiological data indicate that infection of cattle with chlamydiae such as Chlamydophila (C.) pecorum, C. abortus, C. psittaci and Chlamydia suis, is ubiquitous with mixed infections occurring frequently. The apparent lack of association between infection and clinical disease has resulted in debate as to the pathogenic significance of these organisms, and their tendency to sub-clinical and/or persistent infection presents a challenge to the study of their potential effects. However, recent evidence indicates that chlamydial infections have a substantial and quantifiable impact on livestock productivity with chronic, recurrent infections associated with pulmonary disease in calves and with infertility and sub-clinical mastitis in dairy cows. Data also suggest these infections manifest clinically when they coincide with a number of epidemiological risk factors. Future research should: (1) use relevant animal models to clarify the pathogenesis of bovine chlamydioses; (2) quantify the impact of chlamydial infection at a herd level and identify strategies for its control, including sub-unit vaccine development; and (3) evaluate the zoonotic risk of bovine chlamydial infections which will require the development of species-specific serodiagnostics.