Field trial for reducing porcine Taenia solium cysticercosis in Mexico by systematic vaccination of pigs

It has previously been demonstrated that immunization of pigs with a crude extract of Taenia solium metacestodes can confer a high level of protection against an egg challenge. Furthermore, vaccination of infected animals also induces an immune response against the larvae, which are either destroyed or rendered non-infectious. To assess the efficacy of immunization as a strategy for reducing the prevalence of porcine cysticercosis, a field trial of this vaccine was performed in an endemic area in the northern region of the Guerrero State, Mexico, Random samples of pigs belonging to 17 villages were examined for metacestodes by inspection of their tongues. Each animal was immunized with a dose of 150 micrograms of protein (antigenic extract from Taenia solium metacestodes) by the intramuscular route. A prevalence of 2.4% of porcine cysticercosis on average was found in these villages at the beginning of the trial (62 cysticercotic pigs out of 2650 inspected). Six of these villages were selected for the periodic vaccination of new random samples of pigs. A statistically significant decline in the prevalence of porcine cysticercosis was observed at the end of the trial, decreasing from 2.4% at the beginning of vaccination to 0.45% at the end of the trial. A reduction of 82% was observed in spite of the poor living conditions in these villages. These results are consistent with previous data and suggest that it may be possible to turn a susceptible pig population into a protected one by systematic vaccination.

Botulism outbreak associated with poultry litter consumption in three Brazilian cattle herds

One hundred fifty-five of 201 cattle from 3 different farms showed clinical signs and died of botulism after eating the same batch of poultry litter contaminated with poultry and rodent carcasses. The cattle had access to poultry litter for only 1 d; afterwards it was removed from the diet. Death occurred over a period of 17 d after the poultry litter intake. The peak mortality was on day 4; 20 animals died within 10 d of the ingestion. The greater the intake of poultry litter, the higher the cattle mortality. Three steers which died on the first day had peracute effects while the remaining cattle showed classical signs. Twenty-five of the 46 surviving cattle had mild clinical signs, but recovered in a few days. Type C Clostridium botulinum toxin was found in extracts of the poultry litter, carcasses and cattle intestinal contents. Nutrient composition of the poultry litter was normal but pH was lower (6.9) than usual (7.5 to 9.3).

Evaluation of parenteral vaccination methods with glycoproteins against Aujeszky's disease in pigs

A comparative evaluation of vaccination methods with glycoproteins for the induction of immune responses and protection of the pig against Aujeszky's disease virus (ADV) was performed. Different vaccination routes (intradermal (i.d.) versus intramuscular (i.m.)), inoculation sites (the neck versus the back) and number of inoculation points (2 versus 6) per site were compared. Body weight (BW) changes and viral excretion after challenge were compared with virus-neutralizing titers, antigen-specific IgG and IgA responses in serum and virus-specific lymphoproliferative responses in peripheral blood during the immunisation period. According to BW changes better protection was obtained with six-point than two-point i.d. injections. i.d. vaccination in the back at six points gave similar results as i.m. vaccination in the neck but appeared inferior in the reduction of virus excretion. Regarding the immunological parameters, the virus-specific IgA response in serum gave the best indication for protection. It can be concluded that according to BW changes, six-point i.d. immunisation in the back and i.m. immunisation in the neck provided the best protection and that six-point i.d. injections resulted in a better vaccination than two-point i.d. injections.

Baculovirus expressed 2C of foot-and-mouth disease virus has the potential for differentiating convalescent from vaccinated animals

Determining whether animals have been infected with foot-and-mouth disease virus or vaccinated is important because infected animals frequently become carriers of the virus, shed it intermittently and thus may be the source of new outbreaks of the disease. We had shown previously that the sera of convalescent animals contain antibodies to 2C, a highly conserved non-structural protein, whereas the sera of vaccinated animals do not. This is explained by observation that 2C is retained on the membranes of cells used for growing the virus for vaccine production. In contrast, the non-structural protein 3D, which is released into the medium, is not removed by centrifugation or filtration during vaccine production and therefore stimulates an immune response in both vaccinated and convalescent cattle. In this study we produced 2C and 3D in insect cells infected with recombinant baculoviruses. As demonstrated by serology and electron microscopy, 2C is also retained on the membranes of the insect cells. Both expressed proteins react with sera of convalescent animals, indicating that they are conformationally similar, but the 2C does not react with sera from vaccinated animals. The baculovirus expressed 2C appears to be a suitable antigen for the development of a reliable diagnostic test.

The bovine parainfluenza virus type-3 (BPIV-3) hemagglutinin/neuraminidase glycoprotein expressed in baculovirus protects calves against experimental BPIV-3 challenge

Despite the availability of numerous vaccine schedules, "shipping fever", an acute bronchopneumonia brought on in part by a complex of bovine respiratory viruses, remains a major source of economic loss in the beef and dairy industries. We are exploring new strategies of bovine vaccine design which we hope may provide more effective and more cost-efficient control of these pathogens. In this report, we examined the possible use of subunit vaccines, using as an example the hemagglutinin/neuraminidase (HN) protein of bovine parainfluenza virus type-3 (BPIV-3) expressed in the baculovirus expression system. We showed that the protein was expressed at high levels, and was modified to a similar, but not identical size as the native HN protein expressed from BPIV-3 infected bovine cells. We further demonstrated antigenicity and biological activity of the expressed HN protein. Finally, we vaccinated colostrum deprived sera-negative calves with the baculo HN recombinant protein and challenged with BPIV-3. Vaccination induced excellent serum neutralizing antibody responses, and surprisingly, good mucosal antibody responses, even though the vaccine was administered parenterally. The vaccinated animals were well protected against challenge.

Induction of hydrometra in goats by means of active immunization against prostaglandin F2 alpha

Hydrometra is a pathological condition of the uterus which is characterized by accumulation of aseptic fluid in the presence of a persistent corpus luteum. It forms a major cause of subfertility in goats. Active immunization against prostaglandin F2 alpha (PGF2 alpha), the luteolytic hormone in this species, was used to explore the possibility for artificial induction of this pseudopregnant condition. During the breeding season, 11 goats (group I) were immunized with 5 mg PGF2 alpha-ovalbumin conjugate in Freund's complete adjuvant, 4 goats were control-immunized (group CI) and 5 goats remained untreated (group C). Jugular blood samples were taken twice a week (monday and thursday) for measurements of plasma progesterone and binding of 3HPGF2 alpha. In conjunction with blood sampling, transcutaneous ultrasonographic examination of the uterus took place to detect the presence of fluid in the uterus. Before and immediately after immunization, the mean (+/-SD) duration of luteal phases (progesterone concentrations > or = 1 ng ml-1) was 16.7 +/- 1.6 (n = 39), 17.8 +/- 1.3 (n = 23) and 16.9 +/- 1.1 (n = 18) days in animals of group I, CI and C respectively. Ten goats of group I developed an antibody titre. Persistence of luteal function (mean duration +/-SD: 150.3 +/- 23.5 days) occurred in 6 of these animals and in 1 goat of group CI. Accumulation of fluid in the uterus in group I was first observed between day 31 and 38 of the prolonged luteal phase. Discharge of uterine fluid occurred as soon as the plasma progesterone concentration reached a level lower than 0.5 ng ml-1. It is concluded that immunization against PGF2 alpha is an effective method to induce pseudopregnancy in goats, providing a model for studies on luteal maintenance and uterine function in the absence of a conceptus.

Control of blowfly strike in sheep: current strategies and future prospects

Blowfly strike is a cutaneous myiasis in sheep caused by infestations of larvae principally from the family Calliphoridae, particularly the species Lucilia cuprina and Lucilia sericata. These larval infestations cause considerable economic losses to the wool industry. Established control methods have served the industry well in the past, but there are growing deficiencies with these methods. In particular, there is widespread resistance to organophosphorus insecticides and potential difficulties associated with the presence of chemical residues derived from insecticides in wool and waste products which must be disposed of by the industry. There is also growing opposition to the radical surgical procedures used to decrease the susceptibility of sheep to blowfly strike. Consequently, there is a need for the development of alternative control measures. This review examines critically the present control methods and discusses the range of options available for the development of new control strategies. Many of the latter involve novel approaches which will strongly complement current control measures.

Protective immunity to the blood-feeding nematode Haemonchus contortus induced by vaccination with parasite low molecular weight antigens

Partially purified low molecular weight antigens obtained by gel filtration of whole worm homogenates or total adult excretory-secretory (ES) products were tested in a vaccination experiment to determine their ability to induce protective immunity against Haemonchus contortus in sheep. Sheep were challenged with 20,000 infective 3rd-stage larvae. One animal in the low molecular weight vaccinated group showed no protection against H. contortus, whereas the 4 other sheep in this group showed a mean reduction of 99.9% in faecal egg counts and of 97.6% in abomasal worm burden compared to the non-vaccinated controls and the adjuvant controls. The ES-vaccinated sheep showed a 32.2% reduction in parasite egg production and a 63.7% reduction in abomasal worm counts. Analysis of the humoral immune responses revealed no significant differences in antibody recognition of putative protective antigens between the protected and non-protected vaccinated animals. However, a marked lower lymphocyte proliferation response was found in non-protected sheep.

Estimating the rate of pseudorabies virus introduction into pig-finishing herds at regional level

From February to June 1995, 5-12 blood samples were collected in each Dutch pig herd and tested for antibodies against pseudorabies virus (PRV). The percentage of PRV-seropositive pig-finishing herds in three regions with more than 1,000 pigs/km2 (regions 2, 4 and 7) was 6% (region 2), 12% (region 7), and 25% (region 4). The percentage of PRV-seropositive pig-finishing herds in five regions with fewer than 1,000 pigs/km2 (regions 1, 3, 5, 6, and 8) was 3% (region 1), 9% (region 3), 6% (region 5), 0% (region 6), and 4% (region 8). The small sample size allows only the detection of major outbreaks and the percentages of PRV-seropositive herds therefore under-estimate the actual virus circulation in the regions. The fraction of PRV introductions that will result in a major outbreak depends on the herd immunity and thus on the vaccination programme of the herds. By combining for each herd the occurrence or absence of a major outbreak with the herd immunity induced by the vaccination programme, we estimated the average rate at which PRV was introduced into finishing herds in the eight regions. The average number of PRV introductions per finishing herd per finishing period (16 weeks) in the pig-dense regions was estimated at 0.20 in region 2, 0.83 in region 4, and 0.48 in region 7. In the less densely populated regions this rate was estimated at 0.08 in region 1, 0.34 in region 3, 0.17 in region 5, 0.00 in region 6, and 0.09 in region 8. The eight regions could be classified into four areas with a statistically different (P < 0.05 in Mann Whithey U test) rate of PRV introduction: i) regions 1, 6, and 8; ii) regions 2 and 5; iii) regions 3 and 7; and iv) region 4.

Compendium of animal rabies control, 1997. National Association of State Public Health Veterinarians, Inc

This compendium provides information on rabies control to veterinarians, public health officials, and others concerned with rabies control. These recommendations serve as the basis for animal rabies-control programs throughout the United States and facilitate standardization of procedures among jurisdictions, thereby contributing to an effective national rabies-control program. This document is reviewed annually and revised as necessary. Recommendations for immunization procedures are contained in Part I; all animal rabies vaccines licensed by the United States Department of Agriculture (USDA) and marketed in the United States are listed in Part II; Part III details the principles of rabies control.

Nucleic acid vaccination of sheep: Use in combination with a conventional adjuvanted vaccine against Taenia ovis

This report describes the use of a nucleic acid vaccine in a large outbred animal species both alone and in combination with a conventionally adjuvanted vaccine. The gene encoding a host-protective antigen (45W) from the sheep parasite Taenia ovis was cloned into the expression vector pcDNA3 and the resultant plasmid termed pcDNA3-45W. Eleven of 15 sheep injected either intramuscularly or intradermally with pcDNA3-45W mounted a serum antibody response to 45W which for both routes of injection was predominantly IgG1. However, the level of antibody elicited by the nucleic acid vaccine was low and repeated vaccinations did not boost the response. Injection of pcDNA3-45W into animals in which an immune response had previously been generated by vaccination with recombinant 45W using Quil A as adjuvant (rec45W vaccine), did not result in enhanced antibody levels. Initial vaccination with pcDNA3-45W and subsequently with the rec45W vaccine resulted in antibody levels significantly higher (P < 0.05) than those obtained in sheep which had only received the rec45W vaccine. This enhanced antibody response was predominantly of the IgG1 subclass (IgG1 : IgG2, 5 : 1) in animals injected with the nucleic acid vaccine by the i.m. route. Surprisingly, a second rec45W vaccination of these animals led to little or no increase in IgG1 levels and a 10-fold increase in IgG2 resulting in a predominance of 45W-specific IgG2 (IgG1 : IgG2, 0.25 1). These studies revealed that nucleic acid vaccination has efficacy, albeit limited, in the sheep and supports previous investigations which showed that antibody responses elicited by immunization are determined by both the route and mode of antigen delivery.

Postvaccinal immune response to regimens of Newcastle disease vaccination by filter paper sampling technique

Seven hundred and ten blood samples were collected at random from commercial layers in Tamil Nadu on Whatman filter paper No. 1 instead of the conventional method of serum collection. The birds were subjected to different Newcastle disease (ND) vaccination schedules and samples were collected to study the vaccinal response to ND at field level. Eluates were obtained from sample areas of filter paper using Brij-35 solution [detergent] and subjected to the micro haemagglutination inhibition (HI) test for ND antibodies. The HI titre ranged from less than 2(4) to 2(9). The possible causes of poor immune response to ND vaccinations are discussed.

Do postvaccinal sarcomas occur in Australian cats?

A soft tissue sarcoma occurred in the interscapular area of a cat, 1 to 7 months after vaccination at that site. The vaccine contained inactivated feline panleucopaenia virus combined with modified live feline herpesvirus and calicivirus. The tumour showed histological features of both fibrosarcoma and malignant fibrous histiocytoma. The tumour was observed to evolve from the site of a presumed postvaccinal granuloma. Local recurrence 6 weeks post excision necessitated more radical resection. Euthanasia was performed 2 years later when pleural effusion developed. The cause of effusion was not determined. There was no palpable evidence of local tumour regrowth at the time of euthanasia. A causal relationship between vaccination and sarcoma formation is considered based on the temporal association between the two events, the anatomical location of the tumour and histopathology consistent with postvaccinal sarcomas reported overseas. Six other vaccine site fibrosarcomas, potentially vaccine associated using the above criteria, are summarised.

Effects of active immunization against clenbuterol on the growth-promoting effect of clenbuterol in rats

We examined the effect of active immunization against clenbuterol on the growth-promoting effect of clenbuterol in rats in two experiments. Six-week-old female Sprague-Dawley rats were immunized against clenbuterol conjugated to histone by diazotization and then received clenbuterol approximately 4 wk after the initiation of immunization. Antibody titers were determined using indirect ELISA with diazotized clenbuterol-BSA conjugate as an antigen in coating the microwells. Antibody titer increased during booster injections. No significant difference in titer value was observed between two doses of immunogen (.1 vs .5 mg). Competitive ELISA showed that terbutaline cross-reacted with anti-clenbuterol antibodies, and the cross-reactivity was 12%. Alprenolol, propranolol, phentolamine, epinephrine, norepinephrine, and L644,969 showed no affinity for anti-clenbuterol antibodies. The rats immunized against clenbuterol-histone conjugate had 11% lower body weight gain during the 23-d immunization period than the rats immunized against histone only. When clenbuterol was administered after the immunization, no significant difference in growth rate was observed between the rats immunized against clenbuterol-histone conjugate and rats immunized against histone only. No significant difference in muscle weight was observed between the two groups at the termination of the experiment. Results indicate that active immunization against clenbuterol before clenbuterol administration did not modify the growth-promoting effects of clenbuterol in rats.

Protective efficacy of an affinity-purified hemolysin vaccine against experimental swine pleuropneumonia

Protective efficacy of Actinobacillus pleuropneumoniae extracellular hemolytic toxins, RTX-toxin I (Apx I) and Apx II, was evaluated in pigs. The hemolysins were purified from culture supernatant of A. pleuropneumoniae strain HA-337, serotype 1 by immunoaffinity chromatography using a monoclonal antibody specific for Apx I or Apx II as ligand. Four pigs were vaccinated with the purified hemolysins absorbed on aluminum phosphate gel adjuvant. Four pigs of a control group were given placebo. Hemolysin-neutralizing antibodies were detected only in vaccinated group after booster injection. One of four control pigs died following an aerosol challenge with the homologous strain, and three surviving pigs developed serious clinical signs of pneumonia and had extensive lung lesions. In contrast, there was no mortality in vaccinated group. Only transient hyperthermia was observed in two vaccinated pigs after challenge. A necropsy, two vaccinated pigs had slight localized pulmonary lesions, though the remaining two had no lung lesions at all. These results indicate that the hemolysin vaccine made of Apx I and Apx II has good protective activity against swine pleuropneumonia caused by A. pleuropneumoniae serotype.

Estimated prevalence of injection-site sarcomas in cats during 1992

OBJECTIVE

To obtain an estimate of the yearly prevalence of injection-site sarcomas in cats.

DESIGN

Mail survey of members of the American Association of Feline Practitioners.

PROCEDURE

A questionnaire was sent to 1,112 veterinarians.

RESULTS

235 responses were sufficiently complete for inclusion in the study. Overall, responding veterinarians reported 744,993 cat visits in 1992, representing 434,638 individual cats (1.7 visits/cat). The estimated overall prevalence of injection-site sarcomas during 1992 was 0.00021 cases/cat visit (2.1 cases/10,000 cat visits) or 0.00036 cases/cat (3.6 cases/10,000 cats).

CLINICAL IMPLICATIONS

Results suggest that injection-site sarcomas were rare during 1992.

An indirect immunofluorescent test for detection of rabies virus antibodies in foxes

The blood-containing fluids in the thoracic cavity or blood from the heart from 177 red foxes (Vulpes vulpes) in Slovenia were evaluated for rabies antibodies by rapid fluorescent focus inhibition test (RFFIT) and an adapted indirect immunofluorescent test (IIF) in 1994. We evaluated the usefulness of anti-dog fluorescein-isothiocyanate (FITC) conjugate instead of anti-fox FITC conjugate in detection of antibodies against rabies virus in fox sera. In the RFFIT test, 92 (52%) of the fox samples were positive and 70 (40%) samples were negative for rabies antibodies; 15 (8.5%) samples were not suitable for examination in this test. In the IIF test, 98 (55%) fox samples were positive and 79 (45%) sera were negative. The IIF test was suitable for the rapid detection of antibodies against rabies virus in foxes, as often required for vaccine efficacy trials.