Clinical and Serological Response after Experimental Inoculation with Babesia Divergens of Newborn Calves with and without Maternal Antibodies

The influence of maternal antibodies on clinical and serological response after experimental inoculation with Babesia divergens of newborn calves was studied. Five calves, born to dams seropositive for B.divergens, (Group 1) had specific maternal antibodies when tested 12 h after their first feeding of colostrum. At that point they were inoculated i.v. with B.divergens infected erythrocytes. Five other calves, born to dams seronegative for B.divergens, (Group 2) had no Babesia specific maternal antibodies when inoculated at the same age. Babesia divergens organisms were demonstrated in blood smears from calves in both groups at some point 5 to 10 days p.i. All calves in both groups had B.divergens specific IgM antibodies at 7 to 17 days p.i. as shown by a modified IF-test. Specific IgG antibodies, transferred by colostrum, were found in all calves of Group 1 before inoculation of B.divergens. The IgG titre of these animals increased by a doubling dilution step at 11–25 days p.i. Among calves of Group 2 specific IgG antibodies were found at first between day 9 and 15 p.i. Both IgM and IgG antibody titres had to be investigated since demonstrated IgG antibodies can originate both from maternally transferred antibodies and from actively produced antibodies after an infection. There was no difference in clinical parameters; parasitaemia, PCV, Hb, and rectal temperature between the groups. This experiment gives evidence that there can be a resistance to bovine babesiosis in newborn calves independent of maternal antibodies.     

Babesia divergens in France: descriptive and analytical epidemiology

Babesia divergens cause of bovine babesiosis transmitted by Ixodes ricinus, is widely spread especially in West, Central and South-West parts of France. It occurs with two annual peaks, in spring and autumn. The study was carried out during a period of two years (1991-1993) in four farms in the Sarthe area, in order to know the distribution and the ecology of I. ricinus, and to show the presence of B. divergens. Cattle are parasitised as early as March essentially by adult ticks, according to a seasonal distribution (spring, autumn). The flag method allows to catch essentially the larvae and the nymphs on the pastures; nymphs appear as early as March, and larvae one to two months later. Ectoparasite collection on trapped micromammals (Apodemus sylvaticus, Clethrionomys glareolus, etc.) in pastures hedges, is used to detect small I. ricinus populations, mostly larvae. A new ELISA method has been used for the study of the kinetics of anti-B. divergens antibodies in 236 cattle during two years. Most of the animals (60%) show a high antibody level, essentially at the end of the pasture season; the percentage of positive animals decreases during winter and increases again during the pasture season. Calves become seropositive since their first months on pastures. Adults show asymptomatic infections several times along the year, mostly during spring and autumn; only three clinical babesiosis cases have been observed during the whole study, in animals exhibiting nevertheless a high specific antibody level.     

Reproductive and safety assessment of vaccination with Gavac against the cattle tick (Boophilus microplus)

Recent developments in cattle tick control have incorporated the use of recombinant Bm86 vaccines against this ectoparasite. The vaccine developed by our group (Gavac) contains an antigen expressed in Pichia pastoris, and has been successfully employed for the control of tick infestations and transmission of tick-borne diseases. Here, we examined the safety and effect of the Gavac vaccine on reproductive parameters in cattle. Toxicity tests in mice and guinea pigs demonstrated the safety of Gavac. To study the adverse effects of vaccination on reproduction, a field trial involving 9,500 animals in Cuba was conducted. The cattle at 3 farms were vaccinated while those on a fourth farm were left unvaccinated and served as the control. Following vaccination, the control of tick infestation and the transmission of babesiosis were used to demonstrate the efficacy of the vaccine. No adverse effects were observed in any of the reproductive parameters studied when comparing the data before and after vaccination with Gavac and between the vaccinated farms and the control farm. These results demonstrate that under the conditions of our study vaccination with Gavac is safe for use on cattle.     

Immunization of Cattle Against Rabies Using Inactivated Cell Culture Vaccines

Twenty-one heads of cattle were vaccinated with Madibovin, 31 with Rabdomun and 127 with Rabisin on 4 different farms. Rabies neutralizing antibody titre (≥0.5 IU/ml) was detected in 80% of 163 animals tested about 1 month and in 42% of 133 animals tested about 1 year after primary vaccination. On 3 of the farms 86 animals received booster vaccination about 1 year after primary vaccination. All these animals had antibody titre (≥0.5 IU/ml) about 1 month after booster and antibody levels were higher than after the primary vaccination. Rabies antibody titres (≥0.5 IU/ml) were detected in 96% of 50 animals tested 1 year after the booster. No significant differences (p>0.05) in antibody levels were detected between animals vaccinated with Madibovin or Rabisin (farm C) respectively with Rabisin or Rabdomun (farm D) at any collection time. Responses to rabies vaccines varied considerably between the farms. After primary vaccination of the animals on 2 farms with the same batch of Rabisin, the antibody levels clearly differed (p<0.0001) between the farms. Our results indicate that booster is always necessary after primary vaccination to ensure that all animals are protected.     

Effect of vaccination against gonadotropin-releasing factor (GnRF) with Bopriva® in the prepubertal bull calf

The aim of this study was to evaluate the effect of immunization against gonadotropin-releasing factor (GnRF) with Bopriva(?) (Pfizer Animal Health, Parkville, Australia) in prepubertal bull calves. For the study, 6 calves were vaccinated at the age of 3 and 6 weeks with 1 mL Bopriva(?), and 6 animals served as matched controls. Concentrations of GnRF antibodies, testosterone and LH were determined in serum samples out to 30 weeks after the first immunization. Body weight and scrotal circumference were measured for 59 weeks. At slaughter, 65 weeks after the first immunization, the quality of epididymal sperm was evaluated. The results showed that vaccination against GnRF influenced (P<0.05) anti-GnRF titer, LH and testosterone concentrations as well as scrotal circumference. Antibody titers significantly (P<0.05) increased after the booster vaccination and reached peak values 2 weeks later. Compared to control animals, inhibition (P<0.05) of the prepubertal LH secretion was observed in vaccinated calves at weeks 10 and 12-14 after the first vaccination. In vaccinated calves testosterone concentrations decreased after the booster injection to values below 0.5 ng/mL serum and remained for at least 22 weeks at this low level. Animals vaccinated with Bopriva(?) showed a delay in testes growth and smaller scrotal circumference. Puberty occurred at the age between 46 and 55 weeks in vaccinated and between 38 and 52 weeks in control animals and body weight gain was similar in both groups. All vaccinated bulls attained spermatogenic capacity at slaughter when they were 68 weeks old.     

Survival of Oocysts of Eimeria alabamensis on Pastures under Different Climatic Conditions in Sweden

The extent to which oocysts of the coccidian parasite Eimeria alabamensis can survive the winter and cause clinical coccidiosis in different parts of Sweden was investigated. Fecal samples were collected between May and July 1993 from calves on 59 farms where calves had grazed the same pasture for at least 5 consecutive years. The farms were situated in 9 regions of Sweden with different climatic conditions in the winter. On each farm, 5 samples of feces were collected from the floor of the calf-house before the calves were turned out in the spring, and again from the pasture on days 4 or 5, 8 or 9 and 10 or 11 after they were turned out. Overwintering of oocysts of E. alabamensis was considered to have occurred if an increase in the excretion rate of oocysts of this species could be demonstrated 8 to 11 days after calves had been turned out to pastures that had not been grazed since the previous autumn. Oocysts were shown to have overwintered on 27 farms, representing all 9 regions. Samples from 20 (34%) of the farms representing all the climatic regions contained more than 850000 oocysts per g of feces. This was comparable with the numbers found in animals with clinical coccidiosis due to E. alabamensis. Delaying turnout until the beginning of July did not affect the infection rate of the calves. However, calves which were turned out to pastures that had been grazed by older cattle or horses, either earlier in the spring or in previous years, excreted significantly fewer oocysts than calves which were turned out to pastures that had been grazed only by calves. A questionnaire answered by 321 dairy farmers revealed that of the 298 farmers who turned their first-season grazing cattle out to traditional pastures, 179 (60%) had used the same pasture for at least 5 years. These 179 farmers had experienced a significantly higher incidence of diarrhoea in their calves during the first 2 weeks at pasture than those farmers who had used different pastures.     

Vaccination against Feline Panleukopenia: implications from a field study in kittens

ABSTRACT: BACKGROUND: Feline Panleukopenia (FPL) is a serious disease of cats that can be prevented by vaccination. Kittens are routinely vaccinated repeatedly during their first months of life. By this time maternally derived antibodies (MDA) can interfere with successful vaccination and inhibit the development of active immunity. The efficacy of primary vaccination under field conditions was questioned by frequent reports to the Paul-Ehrlich-Institut on outbreaks of FPL in vaccinated breeding catteries. We therefore initiated a field study to investigate the development of immunity in kittens during primary vaccination against FPL. 64 kittens from 16 litters were vaccinated against FPL at the age of 8, 12 and 16 weeks using three commercial polyvalent vaccines. Blood samples were taken before each vaccination and at the age of 20 weeks. Sera were tested for antibodies against feline panleukopenia virus (FPV) by hemagglutination inhibition test and serum neutralisation assay in two independent diagnostic laboratories. RESULTS: There was a good correlation between the results obtained in different laboratories and with different methods. Despite triple vaccination 36.7% of the kittens did not seroconvert. Even very low titres of maternally derived antibodies (MDA) apparently inhibited the development of active immunity. The majority of kittens displayed significant titres of MDA at 8 and 12 weeks of age; in some animals MDA titres that interfered with vaccination were still detected at 20 weeks of age. Interestingly, the vaccines tested differed significantly in their ability to overcome low levels of maternal immunity. CONCLUSIONS: In the given situation it is recommended to quantify antibodies against FPV in the serum of the queen or of the kittens before primary vaccination of kittens. The beginning of primary vaccination should be delayed until MDA titres have declined. Unprotected kittens that have been identified serologically should be revaccinated.     

A Study on the Effects of Tactical Drenchings with a Benzimidazole against Ostertagiasis in Calves

In the present study tactical fenbendazole treatments against ostertagiasis in calves were given at short intervals towards the end of the grazing season. This prevented clinical disease and had moderate effects on parasitic loads in animals that stayed on the same pasture throughout the season. The feasibility of tactical treatments is discussed in relation to various strategical control measures.     

Revaccination of Cattle with Bacille Calmette-Guérin Two Years after First Vaccination when Immunity Has Waned,Boosted Protection against Challenge with Mycobacterium bovis

In both humans and animals, controversy exists concerning the duration of protection induced by BCG vaccine against tuberculosis (TB) and whether revaccination enhances protection. A long-term study was undertaken to determine whether BCG-vaccinated calves would be protected against challenge with Mycobacterium bovis 2½ years after vaccination and to determine the effect of revaccination after 2 years. Seventy–nine calves were divided into five groups (n = 15–17 calves/group) with four of the groups vaccinated subcutaneously with 10⁵ CFU of BCG Danish at 2–4 weeks of age and the fifth group serving as non-vaccinated controls. Three of the four BCG-vaccinated groups were revaccinated 2 years after the initial vaccination. One BCG-vaccinated group was revaccinated with BCG. A second group was vaccinated subcutaneously with a TB protein vaccine consisting of biopolyester particles (Biobeads) displaying two mycobacterial proteins, ESAT-6 and Antigen 85A, mixed with an adjuvant. A third group was vaccinated with TB proteins from M. bovis culture filtrate, mixed with an adjuvant. Twenty-three weeks after the BCG revaccination, all animals were challenged endotracheally with virulent M. bovis and a further 13 weeks later, animals were killed and necropsied to determine protection against TB. The BCG-vaccinated animals produced positive tuberculin caudal fold intradermal (15 of 62 animals) and IFN-γ TB test responses (six of 62 animals) at 6 months after vaccination, but not at subsequent time-points compared to the non-vaccinated animals. Calves receiving a single vaccination with BCG vaccine 2½ years prior to challenge were not protected against TB, while those revaccinated with BCG 2 years after the initial vaccination displayed significant reductions in lung and pulmonary lymph node lesion scores compared to the non-vaccinated animals. In contrast, no reduction in lesion scores was observed in the animals revaccinated with the TB protein vaccines with their immune responses biased towards induction of antibody.     

Persistence of influenza serum antibodies in humans following immunization with a bivalent A/Victoria and A/New Jersey vaccine.

The persistence of serum antibodies 1 year after immunization with a bivalent vaccine containing recombinant viruses that were antigenically identical with A/Victoria/3/75 (H3N2) and A/New Jersey/8/76 (Hsw1N1) viruses was measured in 128 persons aged 18 to 65 years. Serum samples were tested with the hemagglutination inhibition assay against the two vaccine antigens and against A/Texas/1/77 (H3N2) and A/USSR/90/77 (H1N1) viruses. Prior to vaccination 56% and 79% of the participants had been found to be seronegative to A/Victoria and A/New Jersey antigens respectively; the geometric mean antibody titres were low (1:5 to 1:11) except in persons aged 51 to 65 years, whose mean titre of antibody to the A/New Jersey antigen was 1:23, and persons aged 26 to 35 years, whose mean titre of antibody to the A/USSR antigen was 1:25. By 3 weeks after vaccination 85% of the seronegative persons had a fourfold or greater rise in titres of antibodies to the viruses in the vaccine, and 70% had a fourfold increase in titre of antibody to the A/Texas antigen. Of the persons aged 26 to 35 years (seronegative and seropositive) 68% had a fourfold or greater increase in titre of antibody to the A/USSR antigen. There was no change in the mean titres of 19 unvaccinated control subjects during the observation period. At 6 and 12 months after vaccination the titres of antibodies to the A/Victoria and A/New Jersey antigens had declined moderately in all age groups from those observed 3 weeks after vaccination. The rate of decline was similar for the various antibodies except that to the A/USSR antigen in persons 26 to 35 years of age, in whom the decline was much slower.     

Development and testing of a bovine trichomoniasis vaccine

Eighteen culled dairy cows were randomly allocated into 1 of 5 treatment groups. Six cows were vaccinated twice (2V), 21 days apart, 3 with whole cell (2WC) and 3 with fragmented cell membrane (2FC) containing 1 x 10(9)Trichomonas fetus organisms or protein equivalent in a commercial mineral oil adjuvant vaccine. Six more cows were vaccinated once (1V), 3 with whole cell (1WC) and 3 with fragmented cell vaccine (1FC), using the same vaccine, while 6 cows were used as the unvaccinated controls. All cows were challenged with 1 x 10(5) organisms 4 weeks after the second or the only vaccination. After challenge, cervico-vaginal mucus (CVM) samples were cultured for T . fetus weekly for 9 weeks. Whole cell vaccines were superior to fragmented cell vaccines, and both performed better than no vaccination for apparent elimination of trichomonad infections in dairy cows. In addition, 2V was superior to 1V, which, in turn, was superior to no vaccination. Furthermore, clearance time was reduced most by 2V and whole cell vaccination compared with 1V and fragmented cell vaccination. Clearance time was decreased significantly in all vaccinated cows compared with that in unvaccinated cows.     

Assessment of a recombinant F1-V fusion protein vaccine intended to protect Canada lynx (Lynx canadensis) from plague

As part of an ongoing restoration program in Colorado, USA, we evaluated adverse reactions and seroconversion in captive Canada lynx (Lynx canadensis) after vaccination with a recombinant F1-V fusion protein vaccine against Yersinia pestis, the bacterium that causes plague. Ten adult female lynx received the F1-V vaccine; 10 source- and age-matched lynx remained unvaccinated as controls. All of the vaccinated and control lynx remained apparently healthy throughout the confinement period. We observed no evidence of injection site or systemic reactions to the F1-V vaccine. Among vaccinated lynx, differences in log(10) reciprocal antibody titers measured in sera collected before and after vaccination (two doses) ranged from 1.2 to 5.2 for anti-F1 antibodies and from 0.6 to 5.2 for anti-V antibodies; titers in unvaccinated lynx did not change appreciably over the course of confinement prior to release, and thus differences in anti-F1 (P=0.003) and anti-V (P=0.0005) titers were greater among vaccinated lynx than among controls. Although our findings suggest that the F1-V fusion protein vaccine evaluated here is likely to stimulate antibody responses that may help protect Canada lynx from plague, we observed no apparent differences in survival between vaccinated and unvaccinated subject animals. Retrospectively, 22 of 50 (44%; 95% confidence interval 29-59%) unvaccinated lynx captured or recaptured in Colorado during 2000-08 had passive hemagglutination antibody titers >1:16, consistent with exposure to Y. pestis; paired pre- and postrelease titers available for eight of these animals showed titer increases similar in magnitude to those seen in response to vaccination, suggesting at least some lynx may naturally acquire immunity to plague in Colorado habitats.     

Efficacy of a Vaccine Formula against Tuberculosis in Cattle

“Test-and-slaughter” has been successful in industrialized countries to control and eradicate tuberculosis from cattle; however, this strategy is too expensive for developing nations, where the prevalence is especially high. Vaccination with the Calmette-Guérin (BCG) strain has been shown to protect against the development of lesions in vaccinated animals: mouse, cattle and wildlife species. In this study, the immune response and the pathology of vaccinated (BCG-prime and BCG prime-CFP-boosted) and unvaccinated (controls) calves were evaluated under experimental settings. A 10⁶ CFU dose of the BCG strain was inoculated subcutaneously on the neck to two groups of ten animas each. Thirty days after vaccination, one of the vaccinated groups was boosted with an M. bovis culture filtrate protein (CFP). Three months after vaccination, the three groups of animals were challenged with 5×10⁵ CFU via intranasal by aerosol with a field strain of M. bovis. The immune response was monitored throughout the study. Protection was assessed based on immune response (IFN-g release) prechallenge, presence of visible lesions in lymph nodes and lungs at slaughter, and presence of bacilli in lymph nodes and lung samples in histological analysis. Vaccinated cattle, either with the BCG alone or with BCG and boosted with CFP showed higher IFN-g response, fewer lesions, and fewer bacilli per lesion than unvaccinated controls after challenge. Animals with low levels of IFN-g postvaccine-prechallenge showed more lesions than animals with high levels. Results from this study support the argument that vaccination could be incorporated into control programs to reduce the incidence of TB in cattle in countries with high prevalence.     

Age Distribution of Naturally Occurring Acute Babesiosis in Cattle in Sweden

The age distribution of clinical cases of babesiosis reported by local veterinary practitioners was investigated in 1976 and 1981. The first study was based on material collected primarily for identifying the Babesia species, the second on computerized reports from a part of one county in Sweden. The results were similar. Most diseased animals, 135/165 (82%) and 145/161 (90%) respectively, were more than 2.5 years old (cows), while 27/165 (169b) and 12/161 (8%) respectively, were 1–2.5 years old and only 3–4 (2–3%) animals were calves less than 1 year old. This age group, however, probably did not meet the same infection risk as did older animals. Among cows (>2.5 years old) there seemed to be no influence of age on the distribution of clinical babesiosis. Calculation based upon the entire animal population of the county investigated in 1981 revealed that clinical babesiosis was reported about 11 times more often among cows than among heifers and steers. The comparatively high resistance among 1–2.5 year–old cattle may be a function of an inverse age resistance, and/or may be influenced by vaccination against babesiosis on »high risk« farms in Sweden and a lower risk of infection on other farms such that animals tend to escape infection prior to adultness. Babesia organisms were found in 156 of 165 cases (95%) reported as clinical babesiosis.     

The influence of weather and egg contamination on the development of third-stage larvae of Cooperia oncophora on pasture.

The influence of weather and egg contamination on the dynamics of herbage contamination with infective larave of Cooperia oncophora was investigated on artificially contaminated grass plots and in a grazing experiment with 24 first-year grazing calves from May to October 1987 in Lower Saxony, Germany. On the experimental plots the larval translation was highest at the beginning of July and in the second part of September, following high mean weekly temperatures. Between July and September peak recovery of larvae from herbage occurred 4 weeks after contamination. A seasonal pattern of larval translation similar to that on the experimental plots could be demonstrated on the grazed pastures when the number of larvae per m2 of pasture had been adjusted to the previous egg output by means of a contamination index. The resulting 'relative larval density' is regarded as a good indicator for larval development on pasture. From July to September the larval population on pasture resulted mainly from the egg contamination 2-3 weeks earlier. The short persistence of the infective larvae on herbage was probably due to the frequent and heavy rainfall throughout the season, causing a passive washout of larvae into the soil. On single pastures the larval density started to increase within 1 week after the calves had first contact with these fields. The impact of the calves on the distribution of larvae is discussed.     

Efficacy of an Inactivated Porcine Parvovirus (PPV) Vaccine under Field Conditions

Dose response experiments were carried out by vaccinating groups of seronegative gilts (7 months of age) and groups of gilts with residual maternal serum antibodies to PPV (5 months of age). PPV vaccines containing different amounts of inactivated virions were used. Vaccinations were carried out twice with 3 weeks intervals. It was demonstrated, that a single vaccination even with a vaccine with low antigen content elicited an antibody response to PPV in seronegative gilts. The titer values increased after the 2nd vaccination. When the gilts had residual maternal serum antibodies at the time of vaccination the antibody response was generally lower. In some animals the titer values decreased after the 1st vaccination, but except for 2 gilts vaccinated with vaccines with a low antigen content an increase of titer values followed after the 2nd vaccination. During a field trial performed in a herd with enzootic PPV infection all the gilts were vaccinated with PPV vaccine before mating. Blood samples were examined for HI antibodies before and after vaccination and at weaning time of each of the resulting 5 litters. In total 24 batches of gilts comprising 326 animals mated during a 2 year period were examined. It was demonstrated, that the applied vaccine preparations used under field conditions gave a relatively high and long lasting antibody response, even when the gilts were vaccinated as early as at about 5 months of age.     

Immunogenicity and protective efficacy of solubilized merozoite-enriched Theileria sergenti immunogens. I: Protection against homologous stabilate challenge.

Theileria sergenti were isolated from infected erythrocytes by hypotonic lysis, and soluble merozoite antigens were purified by sonication and differential centrifugation. The preparation contained 29, 34, 35 and 105 kD immuno-dominant poly-peptides. The soluble antigens (0.5 mg/ml) were prepared and fortified with Freund's adjuvant. Five month old naive Korean calves were subcutaneously inoculated with the preparation and a booster dose was administered 4 weeks later. Nine weeks after the booster dose, vaccinates and controls were challenged with a homologous stabilate (5.6 x 10(6) RBC/dose, 40% Parasitemia). All animals were monitored for hematocrit, total erythrocyte count, parasitemia and for the specific antibody by Western immunoblot (WB) and indirect immuno-fluorescent antibody (IFA) test. By 18 weeks after vaccination (6 weeks after the challenge), vaccinated cattle had an average IFA titer of 1:10,240 compared with 1:1,280 of the controls. The vaccinates showed negligible change in hematocrit and total RBC count whereas control animals showed significant (p less than 0.05) hematological changes and associated anemia. After vaccination and challenge, the antibody responses demonstrated that vaccination had induced significant production of antibody to the 29 and 35 kD polypeptides. The latter polypeptide was much more strongly recognized by the vaccinated animals, and thus it may be a potential candidate for the vaccine.     

Experiences with vaccination and epidemiological investigations on an anthrax outbreak in Australia in 1997

Between January and February 1997, there was a severe outbreak of anthrax on 83 properties in north-central Victoria, Australia. Vaccination was used as a major tool to control the outbreak by establishing a vaccination buffer zone 30 km by 20 km. In all, 78, 649 cattle in 457 herds were vaccinated in a three week program. In the face of the outbreak, there was a delay before vaccination was able to stop deaths. In the 10 days following vaccination 144 cases of confirmed anthrax occurred and 38 cases occurred more than 10 days after vaccination. When all cattle on at-risk properties were revaccinated in October and early November 1997, there were only two confirmed cases of anthrax in vaccinated seven and nine month old calves in the following anthrax season. Investigations into the epidemiology of the outbreak were unable to establish a single major association for the spread of the disease by flies, biting insects, carrion scavengers, wind, manufactured feed, milk factory tanker routes, veterinary visits, animal treatments, movements of personnel between farms or burning of carcases. The weather conditions in the outbreak area were part of a long dry spell with periods of high daily and night temperatures, continuing high humidity over the period and higher than normal soil temperatures. It is possible that extensive earth works in the district involving irrigated pasture renovation and water channel and drainage renovation could have disturbed old anthrax graves. It is postulated that these works released spores that were dispersed in the preceding wet winter across poorly drained areas that formed the axis for the outbreak. The earth moving renovations establishing irrigation in the area were conducted in the late 1890s, and before the occurrence of anthrax outbreaks were recorded. The axis of the outbreak was the major stock route for cattle and sheep moving from southern Victoria to northern Victoria and southern New South Wales, and undoubtedly there would have been extensive anthrax outbreaks before vaccine became available in the 1890s. In respect of other outbreaks, the events in Victoria most resembled outbreaks of anthrax recorded in the United States of America in the 1950s, 1960s and 1970s.     

Inactivated simian immunodeficiency virus vaccine failed to protect rhesus macaques from intravenous or genital mucosal infection but delayed disease in intravenously exposed animals.

Eight rhesus macaques were immunized four times over a period of 8 months with a psoralen-UV-light-inactivated whole simian immunodeficiency virus vaccine adjuvanted with threonyl muramyl dipeptide. Eight unvaccinated control animals received adjuvant alone. Only the vaccinated animals made antibodies before challenge exposure to the viral core and envelope as determined by Western blotting (immunoblotting) and virus-neutralizing antibodies. Ten days after the final immunization, one-half of the vaccinated and nonvaccinated monkeys were challenged exposed intravenously (i.v.) and one-half were challenge exposed via the genital mucosa with virulent simian immunodeficiency virus. All of the nonvaccinated control monkeys became persistently infected. In spite of preexisting neutralizing antibodies and an anamnestic antibody response, all of the immunized monkeys also became persistently infected. However, there was evidence that the clinical course in immunized i.v. infected animals was delayed. All four mock-vaccinated i.v. challenge-exposed animals died with disease from 3 to 9 months postchallenge. In contrast, only one of four vaccinated i.v. challenge-exposed monkeys had died by 11 months postchallenge.     

Biological control of trichostrongylid infections in calves on pasture in Lithuania using Duddingtonia flagrans, a nematode-trapping fungus

The effect on the pasture contamination level with infective trichostrongylid larvae by feeding the nematode-trapping fungus, Duddingtonia flagrans at two dose levels to first time grazing calves was examined in Lithuania. Thirty heifer-calves, aged 3-6 months, were divided into three comparable groups, A, B and C. Each group was turned out on a 1.07 ha paddock (a, b and c). The paddocks were naturally contaminated with infective trichostrongylid larvae from infected cattle grazing the previous year. Fungal material was fed to the animals daily during a two month period starting 3 weeks after turnout. Groups A and B were given 10(6) and 2.5x10(5) chlamydospores per kg of live weight per day, respectively, while group C served as a non-dosed control group. Every two weeks the heifers were weighed and clinically inspected. On the same dates, faeces, blood and grass samples were collected. From mid-July onwards, the number of infective larvae in grass samples increased markedly (P<0.05)on paddock c, whereas low numbers of infective larvae were observed on paddocks a and b grazed by the fungus treated groups. However, the results indicate that administering fungal spores at a dose of 2.5x10(6)chlamydospores per kg live weight per day did not significantly prevent parasitism in calves, presumably due to insufficient suppression of developing infective larvae in the faeces. In contrast, a dose of 10(6) chlamydospores per kg lowered the parasite larval population on the pasture, reduced pepsinogen levels (P<0.05), and prevented calves from developing parasitosis.