Type D bovine botulism outbreaks associated with poultry litter are increasingly reported in European countries, but the circumstances of exposure to Clostridium botulinum toxins remain unclear. In spring 2015, a large type D/C bovine botulism outbreak affected a farm with dairy and poultry operations. Epidemiological and laboratory investigations strongly suggest that the outbreak was caused by feeding cattle with insufficiently acidified grass silage that was contaminated by type D/C C. botulinum spores. The source of the spores remains unclear, but could have been a stack of poultry litter stored in the grass silage pasture before harvesting. The presence of putrefied poultry carcasses mixed in with the litter is relatively unlikely considering the careful daily removal of poultry carcasses. These findings reinforce the importance of proper ensiling of feed materials and highlight the need for safe disposal of poultry litter, even in the case of good management of poultry deadstock, in order to prevent bovine botulism.

Seventeen four- to five-week-old calves that were not shedding bovine respiratory syncytial virus (BRSV) were vaccinated intranasally against the disease and sampled by nasal swabbing on 16 different days for up to 20 days after vaccination. BRSV vaccine virus was detected in 15 of the 17 calves. Five of the calves were PCR positive on only one swab, eight were PCR positive on two to five swabs and two were PCR positive on more than five swabs. Twelve of the calves were positive only before day 14 and three were positive after day 14. The nasal shedding of BRSV vaccine virus was very variable.

Respiratory disease in cattle is often associated with the youngest animals such as calves, heifers or steers (Hartel et al. 2004; Ames, 1997). Most cases appear before the age of two-years old (if not before the end of the first month of life-Crowe, 2001), and respiratory disease is a major cause of losses, particularly in beef cattle production (Prado et al. 2005; Kapil & Basaraba, 1997; Johnson, 1991).

Introduction Respiratory disorders are usually considered as a major health issue in cattle, particularly in young calves [1, 8, 13]. Among the great number of viruses and bacteria potentially involved, the Bovine Respiratory Syncytial Virus (BRSV) appears to be the most common and significant aetiological agent of respiratory disorders [8, 9, 13]. Oubreaks of BRSV infection mostly occur in nonweaned calves less than three months of age [14]. Currently, the most widespread method of indirect detection of BRSV infection relies on detection of total immunoglobulins G (IgG) specific of BRSV by Enzyme Linked Immunosorbent Assay (ELISA). Evidence of an active immune response to BRSV is a specific rise in titer of total IgG from at least 400% between two blood samples three weeks apart [5]. However, taking into account the very strong seroprevalence of specific BRSV antibodies in cows (between 70% and 95%) the frequency of calves with BRSV specific maternallyderived antibody is very high [4, 9]. Maternally-derived antibody suppresses antigen-specific serum antibody response during the first months of life. So, reliance on paired-serological testing to identify BRSV in calves less than 3 months of age is not recommended [15]. The passively transferred antibodies are mainly of the IgG1 isotype, whatever the etiologic agent concerned [4, 6]. Amount of IgG2 is very low in the colostrum [2, 7, 10]. Moreover, if IgG2 seem to appear only 3 weeks after the infection, they remain detectable during more than 80 days [7, 11, 15]. However, the only study dealing with IgG2 specific of BRSV in calves less than 3 months and in spontaneous BRSV natural infections was carried out on only five calves [11]. This study aimed at describing, under field conditions, the level of total IgG and IgG2 specific of BRSV obtained from a large sample of sera from young calves before and after colostrum intake and from their dams.

Although microbial agents alone do not usually cause disease, they do however play a role in infectious bronchopneumonias of young cattle. Pasteurella organisms are the bacteria most commonly isolated. Two species play a particularly important role: Mannheimia haemolytica and Pasteurella multocida. M. haemolytica (PhA(1), PhA(6)) serotypes 1 and 6 have a number of virulence factors. Leucotoxin plays a determining pathogenic role and is an important immunosupport. Mycoplasma organisms are commonly isolated from the lungs of cattle with respiratory problems. The different species isolated do not have the same pathogenicity. Among the mycoplasms commonly isolated, some do not show pathogenicity or cause a subclinical infection. Only M. bovis has true pathogenicity Pulmonary forms of salmonellosis usually affect intensively reared veal calves. Salmonella typhimurium is the most frequently isolated serovar.

Protection of paratuberculosis-free cattle farms includes checking introduced animals, by direct test for the bacillus by PCR and avian tuberculin intradermal testing. Control of paratuberculosis on infected farms includes elimination of sources of infection (screening of sick animals and asymptomatic excreters using coproculture and serology protocols, a policy of isolation and elimination of positive animals, sterilisation of the environment) and protection of susceptible animals using hygiene measures (isolation of new-born calves and separate management of young cattle) and possible treatment as allowed by the regulations and availability of vaccines. If vaccination is possible, it does not inhibit infection but hinders or slows down the apparition of clinical signs.

The main direct diagnostic tests for M. paratuberculosis are coprobacterioscopy and faecal culture, but provision of results is slow. PCR and mesenteric lymph node biopsy may also be used. There are various indirect immunological methods. The main tests are allergic and not highly specific such as the complement fixation test, indirect immunofluorescence, gel precipitation test and ELISA, the most sensitive technique. None of these tests alone are sufficient to diagnose paratuberculosis. The choice of test depends on the required objective: individual screening or herd testing to confirm suspected clinical cases, to estimate the level of infection or to institute a control programme.

Four stages of clinical paratuberculosis are recognised. Stage I corresponds to the incubation period (in fact, inapparent infection), the duration of which is highly variable. Stage II manifests as non-specific symptoms. The characteristic clinical signs (weight loss, intermittent diarrhoea) are seen during Stage III, which can last for three to four months, and then worsen to become Stage IV (continuous projectile liquid diarrhoea, with neither abdominal pain nor tenesmus, terminal cachexia). The macroscopic lesions that are characteristic of the classical form of the disease affect the intestinal tract (ileum and ileocaecal valve) and the corresponding lymphatic system causing oedematous thickening with inflammation and eventual necrosis. Diagnosis of the condition in the herd is delayed if made simply on observation of the symptoms and lesions.

Bovine para tuberculosis is caused by the presence and multiplication of Johne's disease bacilli (Mycobacterium paratuberculosis) in the wall of the intestine. This bacterium is identifiable by its slow growth, its alcohol-acidic resistance characteristics and its mycobactin dependence. The symptoms observed are caused by the multiplication of the bacilli in the intestine, which provokes an intractable inflammatory and immune reaction. On the farm, paratuberculosis mainly occurs after the introduction of an infected animal but this source is often difficult to establish due to the long incubation period. Contaminated faecal material and environment are sources of the bacilli. The disease is observed in a few infected individuals. The micro-organism is relatively non-pathogenic and the susceptibility of individual animals to infection and development of the disease varies according to a number of intrinsic and extrinsic factors.

In human medicine, insulin-dependent sugar diabetes is considered the result of an autoimmune reaction against pancreatic beta-cells. The autoimmune response is triggered by various factors, such as viral infections. In cattle, BVD/MD has been suspected of provoking such autoimmune reactions. A clinical case that seems to deal with this mechanism is described.

The relationship between the two biotypes of bovine viral diarrhoea virus (BVDV) and the biological responses they induce was studied in 3- to 6-month-old calves inoculated intranasally with a homologous pair of non-cytopathic and cytopathic strains. Marked differences in virological and serological events occurred following exposure to a specific BVDV strain. The non-cytopathic biotype was frequently recovered from nasal secretions and blood cells during the first 28 days post-inoculation whereas the cytopathic counterpart was detected infrequently in nasopharyngeal swabs only. There was no correlation of the recovery of infectious virus in vivo with the biotype-specific neutralizing humoral immune response. Furthermore, seroconversion did not correlate with resistance to reinfection as judged by the transient viraemia and/or shedding of virus observed in a challenge experiment.

A 25 month old Holstein heifer is hospitalised over two months with a delayed growth associated with several chronic conditions. A genetic disease is the origin of this disorder : the BLAD syndrome. Laboratory tests are required to carry out a proper differential diagnosis and rule out a case of chronic BVD. Only genetic analysis can confirm the diagnosis of BLAD (4 photos, 1 figure, 3 tableaux, 1 encadre, 31 references).