Comparative pathogenicity of Theileria annulata strains

Twenty three susceptible crossbred calves were inoculated with five Indian strains of Theileria annulata, collected from natural cases of tropical theileriosis at Ludhiana, Hissar, Jaipur, Uruli-Kanchan and Bangalore. All the strains produced clinical disease with typical symptoms and lesions of acute theileriosis. The strains were considered highly virulent and equally pathogenic.     

Comparative pathogenicity of Theileria annulata strains

Summary

Twenty three susceptible crossbred calves were inoculated with five Indian strains of Theileria annulata, collected from natural cases of tropical theileriosis at Ludhiana, Hissar, Jaipur, Uruli‐Kanchan and Bangalore. All the strains produced clinical disease with typical symptoms and lesions of acute theileriosis. The strains were considered highly virulent and equally pathogenic.     

A comparison in calves of the antigenicity of three strains of bovid herpesvirus 2.

Three strains of bovid herpesvirus 2, viz. Allerton, bovine mammillitis and 69/1LO were used to infect calves intradermally. Twenty-eight days later the immunity of the calves was challenged by intravenous injection of a homologous or heterologous strain. Challenge control calves developed a fever (greater than 40 degrees C) lasting several days and widespread skin lesions which varied with the strain. Homologous challenge of the primary infection produced neither skin lesions nor febrile response, except in one calf in which fever was noted on one day. Heterologous challenge did not cause skin lesions but fever occurred in 8/12 calves. In particular Allerton virus failed to protect completely against heterologous challenge. Despite minor differences evident in these experiments, it is recommended that these isolates should be considered as strains of the same virus--bovid herpesvirus 2.     

Experimentally induced infectious bovine keratoconjunctivitis: resistance of vaccinated cattle to homologous and heterologous strains of Moraxella bovis.

In studies to determine whether vaccination with one strain of Moraxella bovis would protect against challenge with virulent homologous or heterologous strains, calves were intramuscularly inoculated 3 times with formalin-killed M bovis, with 14 days between inoculations. Fourteen days after the 3rd vaccinal dose was given, all calves were exposed to homologous or heterologous virulent cultures of M bovis. The results indicated that vaccination with one strain of M bovis may induce protective immunity against homologous and heterologous challenge exposure; however, because vaccinated cattle resisted infection and disease produced by a homologous strain to a greater extent than they resisted those produced by heterologous strains, polyvalent vaccines or highly immunogenic common antigens may be needed to protect cattle against the numerous strains they might encounter under natural field conditions. There was minimal correlation between the presence of precipitating antibodies against the heterologous strains and the establishment of infection and disease.     

Immunisation with a combination of two complementary feline calicivirus strains induces a broad cross-protection against heterologous challenges

Feline calicivirus (FCV) is characterised by a high degree of antigenic variation potentially compromising vaccine efficacy. Inclusion of several FCV strains or antigens in current vaccines could be a means to improve protection against antigenically distinct isolates. This study evaluated the synergy between two FCV strains (FCVG1 and FCV431) by comparing immunity induced by either strain with that provided by a combination of the two strains against an heterologous challenge with antigenically distant FCV strains (FCV393 and FCV220). Thirty-two SPF kittens were randomly allocated to four groups of eight cats in each group. Groups B, C and D cats were vaccinated once subcutaneously with strains FCVG1, FCV431, and FCVG1 + FCV431, respectively. Each kitten received a total dose of 10(3.4) CCID50 of FCV. Control group A was not immunised. On day 31, four cats from each group were challenged oronasally with FCV220 and four cats with FCV393. Following challenge, the cats were monitored for clinical signs, viral shedding and antibody responses. FCV220 and FCV393 induced severe clinical signs in control cats typical of FCV infection. Immunisation with both strains mixed together induced higher neutralizing antibody titres against FCV220 and FCV393 strains on average. Protection was observed in all groups, however combination of the two strains resulted in a better clinical protection and reduction of virus shedding after heterologous challenge. A moderate correlation was observed between neutralizing antibody titres at the time of challenge and protection against clinical signs. These results indicated that vaccines combining antigens from different FCV strains may induce a broader heterologous protection.     

Vaccination against infectious bovine keratoconjunctivitis: protective efficacy and antibody response induced by pili of homologous and heterologous strains of Moraxella bovis

The protective effect of 2 Moraxella bovis pili vaccines against infectious bovine keratoconjunctivitis (IBK) experimentally induced by homologous or heterologous strain challenge with virulent, haemolytic M. bovis strain, Dal 2d, was measured in trials using weaned calves aged 3 to 7 months. Purified pili vaccines were prepared from haemolytic strain Dal 2d, (pilus serogroup IV), and haemolytic strain Epp 63, (pilus serogroup III). Calves were challenged by conjunctival instillation of 1 x 10(9) colony forming units of virulent M. bovis strain Dal 2d 14 days after the second of 2 subcutaneous doses of vaccine. Each consisted of 200 micrograms of pili in alum-oil adjuvant administered at an interval of 21 days. In trial 1 the level of protection against challenge with the homologous strain was 46.7% (p less than 0.01). Small, rapidly resolving lesions of IBK occurred in some vaccinates compared with a larger proportion of severe lesions that required treatment in non-vaccinated calves (p less than 0.025). In trial 2, the level of protection against IBK after exposure of vaccinates to the homologous Dal 2d strain was 72.7%, but no significant level of protection or reduction in the size and duration of lesions was apparent in similarly challenged calves vaccinated with Epp 63 pili when contrasted with susceptible, non-vaccinated controls. No marked reduction in the duration of infection with M. bovis Dal 2d following challenge resulted from vaccination with pili of either of the serogroups III or IV. Rising homologous serum IgG antibody titres to serogroups III and IV pili were recorded in response to vaccination with each antigen.(ABSTRACT TRUNCATED AT 250 WORDS)     

Studies on cross protection induced in calves by rotaviruses of calves, children and foals.

Inoculation at birth with a live attenuated strain of a bovine rotavirus isolated in the USA (scourvax-reo) induced protection in five gnotobiotic calves seven to 21 days later against a UK isolate of pathogenic bovine rotavirus. However, no protection was induced in three calves challenged three to five days after vaccination. There was a close antigenic relationship demonstrated between the two bovine rotavirus isolates. In contrast only one of three gnotobiotic calves inoculated with foal rotavirus, and one of three with human rotavirus, were protected against bovine rotavirus challenge. Protection in these two calves correlated with high heterologous immunofluorescent antibody titre (320 or greater), although the neutralising antibody titres was less than 20.     

Genetic variation and cross-reactivity of Clostridium septicum alpha-toxin

Clostridium septicum alpha-toxin genes were sequenced with the polymerase chain reaction (PCR) products amplified from DNAs of 25 C. septicum strains, and were classified into 10 patterns. Alpha-toxins were purified from the culture supernatant of four C. septicum strains (strains No. 44, Kagoshima 8, Mie and Tokachi) which were specially chosen from patterns of the deduced amino acid sequences. The molecular weights of the alpha-toxins were not different according to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis. However, the isoelectric points between the alpha-toxins of No. 44 and Tokachi strains differed markedly. Cross-neutralization tests were performed with purified alpha-toxins and antitoxins in mice and in Vero cells. Each antitoxin showed roughly the same titers against the four alpha-toxins in mice and completely identical titers against these in Vero cells. Calves immunized with toxoid prepared from the culture supernatant of No.44 strain were challenged by exposure to spores of Mie strain. The toxoid conferred protection against the challenge in calves. From these results, although genetic variation has been observed within the C. septicum alpha-toxin gene, C. septicum strains toxoid of strain No.44 induces protective immunity against exposure to C. septicum that produce other subtypes of alpha-toxin containing several different amino acid residues.     

Safety and efficacy of an oil-adjuvant vaccine against haemorrhagic septicaemia in buffalo calves: cross-protection between the serotypes B:2,5 and E:2,5.

The safety, efficacy and duration of immunity of an improved oil-adjuvant vaccine against haemorrhagic septicaemia, containing inactivated cells of Pasteurella multocida serotype B:2,5, were tested in young buffalo calves in Pakistan. For safety testing, five buffalo calves were vaccinated intramuscularly with twice the normal dose, and six weeks later with a normal dose. Except for a transient rise in rectal temperature at six hours after the vaccinations, no systemic reactions were observed. The buffaloes remained in good condition and had a normal appetite. No local reactions were observed at the injection site. For efficacy testing two trials were carried out. In the first, buffalo calves were vaccinated intramuscularly either with two doses two-and-a-half months apart, or with a single dose, or left unvaccinated. They were challenged subcutaneously with virulent P multocida after eight, 13 or 15 months. After challenge at eight months the four buffaloes given two doses and the buffalo given one dose were protected, whereas the control animal developed the typical signs of the disease. After the challenges at 13 and 15 months, the vaccinated animals were still protected whereas the control animals died. In the second trial, buffalo calves were vaccinated intramuscularly either with two doses two months apart, or with a single dose at two months or left unvaccinated. The buffaloes were challenged after eight or 14 months. After challenge at eight months the four control animals died, whereas three of the four buffaloes given a single dose were protected. After challenge at 14 months, the three control animals died, whereas four of the five buffaloes given two doses and both the buffaloes given a single dose were protected. To test for cross-protection against the heterologous serotypes E:2,5 and B:3,4, groups of mice were vaccinated once or left unvaccinated. Four weeks later, the vaccinated and control groups were challenged with a dilution series of the different challenge cultures. The vaccine appeared to induce protection against challenge with different strains of serotypes B:2,5 and E:2,5 but not against strains of serotype B:3,4.     

Intramuscular vaccination of young calves with a Salmonella Dublin metabolic-drift mutant provides superior protection to oral delivery

In homologous and heterologous challenge trials using calves 相似文献   

Theileria parva: the immune status of calves born of dams immunised against East Coast fever

Eight Friesian cross cows three months pregnant to a single Friesian bull were immunised against East Coast fever by infection with Theileria parva (Muguga) sporozoite stabilate and treatment with pyrrolidino-methyl tetracycline. They were challenged with the homologous stock four times before calving and a fifth time after calving, and resisted all five challenges which killed all of the five groups of five susceptible controls. Calves born to these hyperimmunised dams were fully susceptible on challenge with the same stabilate, as were susceptible cows from the same farm and their calves. In both instances the calves died three to seven days earlier than the cows which were approximately 10 times heavier. These results show that one- to two-month-old taurine calves from artificially immunised dams are not protected from experimental T parva sporozoite challenge and that there is no inherent calfhood resistance to East Coast fever.     

Efficacy of Fostera PRRS modified live virus vaccine against a Canadian heterologous virulent field strain of porcine reproductive and respiratory syndrome virus

Vaccination is a useful option to control infection with porcine reproductive and respiratory syndrome virus (PRRSV), and several modified live-PRRSV vaccines have been developed. These vaccines have shown some efficacy in reducing the incidence and severity of clinical disease as well as the duration of viremia and virus shedding but have failed to provide sterilizing immunity. The efficacy of modified live-virus (MLV) vaccines is greater against a homologous strain compared with heterologous PRRSV strains. The objective of this study was to evaluate the efficacy of Fostera PRRS MLV vaccine in protecting against challenge with a heterologous field strain widely circulating in the swine herds of eastern Canada. Forty-six piglets were divided into 4 groups: nonvaccinated-nonchallenged; nonvaccinated-challenged; vaccinated-challenged; and vaccinated-nonchallenged. The animals were vaccinated at 23 d of age with Fostera PRRS and challenged 23 d later with a heterologous field strain of PRRSV (FMV12-1425619). Overall, the vaccine showed some beneficial effects in the challenged animals by reducing the severity of clinical signs and the viral load. A significant difference between nonvaccinated and vaccinated animals was detected for some parameters starting 11 to 13 d after challenge, which suggested that the cell-mediated immune response or other delayed responses could be more important than pre-existing PRRSV antibodies in vaccinated animals within the context of protection against heterologous strains.     

Bacterial survival, lymph node changes, and immunologic responses of cattle vaccinated with standard and mutant strains of Brucella abortus.

Forty-eight cattle were used in 4 experiments; 6-week-old calves in experiments 1-3 (n = 24) and 10-month-old heifers in experiment 4 (n = 24). In experiments 1-3, 7 groups of 3 calves each were inoculated SC with 5 strains of Brucella abortus: virulent strain 2308 (2 groups), vaccine strain 19 (2 groups), and mutant strains RB51. 19 delta 31K, and 19 delta SOD. Sera and lymph node tissues were examined at 2-week intervals for evidence of infection. At postinoculation (PI) week 12, 2 calves in each group were given dexamethasone for 5 days. Calves were then euthanatized and lymphoid tissue, spleen, liver, and bone marrow were examined for evidence of B abortus. Calves given strain 2308 had large numbers of bacteria in their lymph nodes, marked granulomatous lymphadenitis in the deep cortex, and loss of lymphoid cells in superficial cortical areas. In addition, they had high serum antibody titers at PI week 16. Calves given strain 19, or genetic mutants derived from strain 19, cleared bacteria from lymph nodes more rapidly, had less lymphoid destruction, and developed antibody titers that did not persist for 16 weeks. The RB51 strain (rough) was cleared most rapidly from lymphoid tissues and induced serum antibody responses only to the core of the lipopolysaccharide molecule. Treatment of calves with dexamethasone did not cause B abortus to reappear in tissues of any calves, nor did serum antibody titers increase.(ABSTRACT TRUNCATED AT 250 WORDS)     

A study on neonatal calf diarrhea induced by rotavirus

This review summarizes the results of a study on rotaviruses isolated from calves affected by neonatal diarrhea.

The results indicated that rotavirus infection is widespread and supported the evidence for an etiologic role of these viruses in neonatal diarrhea. Differences in virulence among bovine rotaviruses appeared also to be confirmed.

Conventionally reared calves were fully susceptible to the experimental infection induced by rotaviruses originating from heterologous hosts, i.e. monkeys, pigs and rabbits.

When rotavirus strains of bovine, simian and rabbit origin were compared by cross neutralization tests, it was found the simian and porcine strains were indistinguishable and both appeared to relate antigenically to the bovine strain.

Finally, it was proven that feeding newborn calves with colostrum and first milk of their dams, previously vaccinated with an inactivated adjuvanted rotavirus vaccine, could prevent the neonatal diarrhea from occurring.     

Experimental transmission of bovine papilloma virus (BPV) extracted from morphologically distinct teat and cutaneous lesions and the effects of inoculation of BPV transformed fetal bovine cells.

Bovine papilloma virus (BPV) was extracted from five cattle each affected with only one of five morphologically distinct lesion types. When inoculated into experimental calves either by scarification or intradermal injection, the BPV extracts produced lesions macroscopically and microscopically similar to those from which individual extracts were made. Fetal bovine cells, transformed in vitro with BPV, failed to produce fibromas, fibropapillomas or papillomas when inoculated into experimental calves. When calves inoculated with virus or BPV transformed cells were challenged with the five original BPV extracts, a differential immunity was demonstrated, while control calves were susceptible to all extracts. Post mortem examination revealed the presence of upper alimentary tract papillomas in three of eight calves forming one group. These results suggest that different strains of BVP, causing morphologically separable lesion types, exist. There may be additional BPV variants causing fibropapillomas of the teat and anogenital regions of cattle. The inoculation of BPV transformed fetal bovine cells conferred a relative immunity to later challenge with some but not all BPV extracts.     

The effect of intramuscular administration of colistin on the development and course of experimentally induced oedema disease in weaned piglets

Shiga-toxigenic E. coli (STEC) strains that produce Shiga toxin Stx2e cause oedema disease in weaned piglets. The purpose of the present study was to investigate the impact of Stx2e released in mesenteric lymph nodes on disease pathogenesis. Colistin and ampicillin were intramuscularly administered to piglets of the experimental group simultaneously challenged with STEC strain, type O139:F18ab, Stx2e+. Piglets of the control group were challenged with STEC only. The strain was naturally resistant to ampicillin and susceptible to colistin. After the challenge, colonisation of the intestines was observed in both antibiotic-treated piglets and control piglets without antibiotic treatment. Histochemistry and scanning electron microscopy revealed sporadic colonisation of the small intestine in the piglets. STEC was detected in the mesenteric lymph nodes of untreated piglets. The clinical manifestations of oedema disease were observed in both groups. In the antibiotic-treated group (11 piglets), oedema disease developed in 10 piglets, eight of which died or were euthanized ante finem. In the untreated group (11 piglets), oedema disease developed in five piglets, four of which died or were euthanized ante finem. We therefore propose that the STEC lysed by colistin suddenly released the toxin from bacterial cells immediately after their passage through the intestinal wall. That could explain a more severe course of oedema disease in the treated piglets. Even though high amounts of STEC were present in the lymph nodes of untreated piglets, the toxin was not released abruptly because the bacterial cells were not damaged.     

Prevention of experimental haemorrhagic septicaemia with a live vaccine

Pasteurella multocida serotype B:3,4 isolated from a fallow deer in England was used as a vaccine to prevent haemorrhagic septicaemia. The deer strain was less virulent for calves than typical serotype B:2 of haemorrhagic septicaemia strains. It elicited antibodies in cattle that protected mice against serotype B:2 infection. The live deer vaccine containing 2 X 10(7) viable organisms per dose was used to immunise calves. Six months after vaccination, five of six calves were protected against serotype B:2 challenge. Two calves challenged nine months after vaccination survived the same challenge. The live vaccine was more efficacious than an alum precipitated vaccine in protecting calves against B:2 challenge.     

Neonatal calf diarrhea induced by rotavirus

This presentation summarizes the results of a comprehensive study on rotaviruses isolated in Italy from calves and rabbits affected by neonatal diarrhea. The results clearly indicated that rotavirus infection is widespread and supported the evidence for an etiologic role of these viruses in neonatal diarrhea. The evidence of differences in virulence among bovine rotaviruses appeared also to be confirmed. Conventionally reared calves were fully susceptible to the experimental infection induced by three rotaviruses originating from heterologous hosts, i.e. monkeys, pigs and rabbits, respectively. When rotavirus strains of bovine, simian, porcine and rabbit origin were compared by cross neutralization tests, it was found the simian and porcine strains were indistinguishable and both appeared to relate antigenically to the bovine strain. On the other hand, a reciprocal antigenic correlation was found between bovine and rabbit isolates. Finally, it was proven that feeding newborn calves with colostrum of their dams, previously vaccinated with an inactivated rotavirus vaccine, could prevent the neonatal diarrhea from occurring.     

DEVELOPMENT OF A HIGHLY INFECTIVE BABESIA BIGEMINA VACCINE OF REDUCED VIRULENCE

The virulence of a strain of Babesia bigemina was reduced by syringe passaging at 3 to 16-week intervals in a series of 7 calves. The calves were splenectomised 1 to 14 weeks after inoculation to induce the relapse parasitaemias used for passaging. Parasites taken at relapse from the last 3 calves in the series were inoculated into splenectomised calves from which highly parasitised blood for vaccine was obtained.
The vaccine produced mild infections in 32 recipient cattle. When challenged either 5 weeks or 7 months after vaccination, the cattle had substantial immunity to a heterologous strain of B. bigemina .     

Intestinal infection following aerosol challenge of calves with Mycobacterium avium subspecies paratuberculosis

ABSTRACT: A challenge experiment was performed to investigate whether administration of Mycobacterium avium subsp. paratuberculosis (MAP) via the respiratory route leads to MAP infection in calves. Eighteen calves from test negative dams were randomly allocated to four groups. Six calves were challenged with MAP nasally and six calves were challenged by transtracheal injection; three orally challenged calves served as positive controls, and three non challenged calves as negative controls. The challenge was performed as a nine-fold trickle dose, 107 CFU in total. Blood and faecal samples were collected frequently. Calves were euthanized three months post-challenge and extensively sampled. Blood samples were tested for the presence of antibodies and interferon gamma producing cells by ELISA. Faecal and tissue samples were cultured in a liquid culture system and the presence of MAP was confirmed by IS900 realtime PCR. Fourteen out of fifteen calves had no MAP antibody response. The negative controls remained negative; all positive controls became infected. Two nasally challenged calves showed a Purified Protein Derivative Avian (PPDA) specific interferon gamma response. In all nasally challenged calves, MAP positive intestinal samples were detected. In three calves of the nasal group MAP positive retropharyngeal lymph nodes or tonsils were detected. In all calves of the transtracheal group MAP positive intestinal tissues were detected as well and three had a MAP positive tracheobronchial lymph node. These findings indicate that inhalation of MAP aerosols can result in infection. These experimental results may be relevant for transmission under field conditions since viable MAP has been detected in dust on commercial dairy farms.