The association of Streptococcus equi subsp. zooepidemicus with canine infectious respiratory disease

Canine infectious respiratory disease (CIRD) is a multi-factorial infection that affects many kennelled dogs despite the wide use of vaccination. Current vaccines aim to protect against viral agents and a single bacterial agent, Bordetella bronchiseptica. We sought to examine the role of streptococcal species in CIRD. The isolation and identification of streptococci in the lower respiratory tract of clinically healthy dogs and those with CIRD were used to correlate the presence of specific streptococcal species with respiratory disease. In this study we report that the presence of S. equi subsp. zooepidemicus is associated with increasing severity of disease in a population of kennelled dogs with endemic CIRD.     

Recent increase of Marek's disease in Korea related to the virulence increase of the virus

The incidence of Marek's disease (MD), an important neoplastic disease of chickens, suddenly increased in 1997 in Korea. Most MD cases of this country were detected in chickens over 20 wk of age. Five MD viruses were isolated from field flocks in which severe MD losses had occurred, and one of the viruses was studied to compare its pathotype with the prototype JM strain. The isolate KOMD-IC induced severe depression not only in body weight but also in relative bursal weight, and the depression by KOMD-IC was more severe than that induced by JM strain. In addition, the incidence of MD tumor caused by KOMD-IC was higher than that caused by the JM strain. The protective capacity of several MD vaccines was studied against challenge with KOMD-IC. The protective levels of several MD vaccines such as herpesvirus of turkeys (HVT), HVT plus SB1, and Rispens were usually lower against challenge with KOMD-IC than those challenged with JM strain, even if the chickens vaccinated with serotype 1 were not completely protected against challenge with KOMD-IC. The above results indicate that the virulence of KOMD-IC isolated recently was increased, and the increase of MD outbreak in Korea may be related to the virulence increase of the virus. Various MD vaccine programs were applied to reduce MD loss to a broiler breeder farm where severe MD loss had occurred. Serotype 1 vaccine could dramatically decrease the mortality due to MD, and the best results were obtained from the flocks vaccinated with bivalent vaccine of Rispens and HVT.     

Antibody-induced internalization of viral glycoproteins in pseudorabies virus-infected monocytes and role of the cytoskeleton: a confocal study

Addition of pseudorabies virus (PrV)-specific polyclonal immunoglobulins to PrV-infected monocytes induces internalization of plasma membrane anchored viral glycoproteins. This process may interfere with antibody-dependent cell lysis and resembles the well-studied physiological endocytosis process. A confocal study was designed to investigate whether the major cellular components, involved in physiological endocytosis (clathrin, actin, dynein and microtubules), play a role in this virological internalization process. In order to visualize the interaction of endosomes, which contain the internalized viral glycoproteins, with clathrin, actin, dynein and microtubules, a double labeling of viral glycoproteins and different cellular proteins was performed. Porcine monocytes were inoculated with the PrV-strain 89V87 at a multiplicity of infection of 50 for 13h. After the addition of FITC-labeled porcine polyclonal PrV-specific antibodies, cells were fixed with para-formaldehyde at different time points and afterwards permeabilized. The different cellular components were visualized with monoclonal antibodies and a Texas Red-conjugate, with the exception of actin, which was stained with phalloidin-Texas Red. The cells were analyzed by confocal microscopy. A clear co-localization was observed between the viral glycoproteins and clathrin and dynein during the internalization process. The microtubules were in close contact with the internalized vesicles. For actin no co-localization could be observed. It can be stated that clathrin, dynein and microtubules, important components during physiological endocytosis, are also of importance during the antibody-induced internalization of viral glycoproteins.     

Simultaneous intramammary and intranasal inoculation of lactating cows with bovine herpesvirus 4 induce subclinical mastitis

In this study, we examined whether an experimental bovine herpesvirus 4 (BHV4) infection can induce bovine mastitis, or can enhance bovine mastitis induced by Streptococcus uberis (S. uberis). Four lactating cows were inoculated intramammarily and intranasally with BHV4, and four lactating control cows were mock-inoculated. After 14 days, two of four cows from each group were inoculated intramammarily with S. uberis. No clinical signs were recorded in cows inoculated only with BHV4, and their milk samples showed no abnormal morphology, despite the fact that BHV4 replicated in inoculated quarters. Somatic cell count increased significantly in milk from three of six BHV4-inoculated quarters, compared to the non-inoculated quarters of the same cows (within-cow) and the quarters of mock-inoculated cows (control group) on days 8, 9 and 11 post-inoculation (pi). BHV4 was isolated from nasal swabs between days 2 and 9 pi. Clinical mastitis was observed in all four cows intramammarily inoculated with S. uberis. A preceding BHV4 infection did not exacerbate the clinical mastitis induced by S. uberis. S. uberis infections appeared to trigger BHV4 replication. From one quarter of each of two cows inoculated with BHV4 and S. uberis, BHV4 was isolated, and not from quarters inoculated with BHV4 only. In conclusion, BHV4 did not induce bovine clinical mastitis after simultaneous intranasal and intramammary inoculation. However, the BHV4 infection did induce subclinical mastitis in 50% of the cows and the quarters.     

Herd-level diagnosis for Salmonella enterica subsp. enterica serovar Dublin infection in bovine dairy herds

Herd-level sensitivities of bacteriological and serological methods were compared in 79 bovine dairy herds, recently infected with Salmonella enterica subsp. enterica serovar Dublin. All farms experienced clinical signs of salmonellosis for the first time and had no history of vaccination against salmonellosis. At the start of the study, infection with serovar Dublin was confirmed with at least one positive bacteriologic culture for serovar Dublin from a clinical case (gold standard for herd infection).Bacteriological culture was done on samples of dung-pits, drinking water, bulk-milk filters, and faeces of animals with current or earlier clinical signs of salmonellosis. Blood samples of all animals and bulk-milk samples were tested using an ELISA.Herd-level sensitivity (HSe) of culture of dung-pits, drinking water, bulk-milk filters, and faeces of animals with current or earlier signs of salmonellosis was 45, 5, 7, and 38%, respectively. HSe for serology of all animals was 100%. If blood samples of all calves 4-6 months old were examined, at least one calf was seropositive on 91% of the infected farms. If serology was performed on samples of animals with current or earlier signs of salmonellosis, at least one animal was seropositive on 80% of the infected farms. HSe for bulk-milk samples was 54%. However, if clinical signs of salmonellosis were observed only in lactating animals, sensitivity of bulk-milk serology was 79%.Interesting combinations of methods were the combination of serology of bulk milk with either serology of animals with current or earlier signs of salmonellosis (HSe=91%), or serology of all calves of 4-6 months old (HSe=99%).     

Effect of preculture freezing and incubation on bacteriological isolation from subclinical mastitis samples

In this study the sensitivity of three methods of isolation of udder pathogens from milk samples from subclinical mastitis cases was compared. For analysis 1827 quarter milk samples were selected. Milk was cultured using a standard culture technique (0.01 ml of fresh milk streaked on a sheep blood agar plate and on Edward's medium). In addition, an inoculum of 0.01 ml of the original milk sample was incubated for 24h at 37 degrees C in broth, followed by culture using the standard culture technique. In the third method, the whole milk sample was frozen for 24h, and then incubated for 24h at 37 degrees C, followed by culture using standard culture technique. The isolation percentage of Staphylococcus aureus was 4.7% for standard culture technique, 14.2% for incubation in broth, and 21.5% for the combination of freezing plus incubation. Isolation percentage of Streptococcus dysgalactiae and Streptococcus agalactiae was highest using the standard culture technique, while isolation rate of Streptococcus uberis was not different among the three methods used. With increasing somatic cell count, the likelihood of S. aureus, S. dysgalactiae and S. uberis isolation increased.Based on the relative sensitivity, defined as the isolation rate using a single technique compared to the isolation rate of the three techniques together, a combination of standard culture technique and freezing plus incubation was most attractive for achieving a high isolation rate of S. agalactiae and S. dysgalactiae. Relative sensitivity of S. uberis isolation was highest using the standard culture technique and incubation in broth, while S. aureus was most often isolated using a combination of incubation in broth and freezing plus incubation. A combination of the three methods increased the isolation rate for S. dysgalactiae, S. uberis and S. aureus. The standard culture technique, together with the combination of freezing plus incubation, can be recommended for isolating major udder pathogens. If S. aureus is the pathogen of main interest, using incubation in broth together with the combination of freezing plus incubation performed best.     

Cooperia punctata trickle infections: parasitological parameters and evaluation of a Cooperia recombinant 14.2 kDa protein ELISA for estimating cumulative exposure of calves

We examined the effects of isoquinoline alkaloids in vitro in an effort to identify a treatment for Strongyloides stercoralis larva migrans in humans. Infective third-stage larvae of S. ratti and S. venezuelensis were used as model nematodes for S. stercoralis. Nematocidal activity was evaluated by the 50% paralysis concentration (PC(50)). Most of the tested isoquinoline alkaloids had activity for S. ratti and S. venezuelensis. We then evaluated in vitro cytotoxicity, which was the 50% inhibition concentration (IC(50)) of the compounds using HL60 tissue-culture cells. Three of the compounds (protopine, D-corydaline, and L-stylopine) which exhibited strong nematocidal activity, showed little cytotoxicity. In addition, we examined the relationship between nematocidal activity and cytotoxicity using the PC(50)/IC(50) ratio. A ratio equivalent to or lower than that calculated for the currently prescribed strongyloidosis treatments, ivermectin, albendazole and thiabendazole, was observed for allocryptopine, protopine, dehydrocorydaline, D-corydaline, L-stylopine, and papaverine. In contrast, the PC(50)/IC(50) ratios for protopine, D-corydaline, and L-stylopine were substantially more favorable. Therefore, protopine, D-corydaline, and L-stylopine were identified as potential effective treatments for strongyloidosis.