Gonadotropin-releasing hormone increases CD4 T-lymphocyte numbers in an animal model of immunodeficiency.

BACKGROUND: Gonadotropin-releasing hormone (GnRH) possesses immunostimulatory properties. We have previously demonstrated that GnRH antagonists decrease lymphocyte numbers in an animal model of autoimmune disease. We speculated that the converse might be true, that GnRH administration would increase lymphocyte numbers or alter lymphocyte subsets in an immunodeficiency state. OBJECTIVE: Our purpose was to test the hypothesis that GnRH agonist would increase IgG and CD4 counts in a rat model of immunodeficiency independently of gonadal steroids. METHODS: We used diabetes-prone (DP) BB rats. This model has been characterized to have an AIDS-like lymphocyte profile, with lymphopenia and depressed CD4 counts. Ovariectomized female DP rats were randomized to receive subcutaneous injections with GnRH or vehicle 6 times weekly. DR rats were ovariectomized and treated with vehicle as controls. We performed flow cytometric analysis and complete blood cell counts at baseline, 3.5 weeks, and 7 weeks of treatment. We also measured total serum IgG and luteinizing hormone levels. RESULTS: GnRH administration significantly increased total serum IgG levels in DP rats compared with vehicle. The percentages of CD4(+) cells in blood were also significantly increased in the GnRH-treated group compared with the vehicle-treated group and compared with baseline. Similarly, the absolute numbers of CD4(+) positive T cells were increased over controls at 7 weeks. The effects of GnRH were specific for the CD4 subset because there were no significant differences in numbers of CD8(+) positive cells between the 2 treatment groups. CONCLUSION: GnRH shows potential utility as an immunostimulatory agent in immunodeficient states manifesting diminished numbers of immunocompetent CD4(+) T lymphocytes.

Effects of inoculations with Eimeria zuernii on young calves treated with decoquinate or narasin with or without dexamethasone.

Sixteen 7-week-old Holstein male calves were inoculated with sporulated oocysts of Eimeria zuernii. Four calves (controls) were euthanatized and necropsied at 14 and 20 days after inoculation (DAI). Two calves were treated with 20 mg of dexamethasone (IM) on 13, 14, and 15 DAI and euthanatized and necropsied 17 DAI and 2 calves were given similar treatments and necropsied 20 DAI. The 8 other calves were euthanatized and necropsied 20 DAI. Two were started on the anticoccidial drug decoquinate in feed 13 DAI; 2 others were given decoquinate on the same schedule plus dexamethasone on 13,14, and 15 DAI. Two calves were given the antibiotic narasin in feed beginning 13 DAI and 2 calves were given parasin on the same schedule plus dexamethasone on 13,14, and 15 DAI. All calves, except 2 controls necropsied 14 DAI and 4 calves given decoquinate, discharged moderate-to-large numbers of oocysts in feces and had moderate-to-serve changes in fecal consistency. Histologic examinations revealed large numbers of endogenous stages in tissues of calves treated or not treated with dexamethasone. Few endogenous stages were observed in tissues from calves that were given decoquinate or decoquinate plus dexamethasone. Calves given narasin or narasin plus dexamethasone had moderate-to-large numbers of endogenous stages in the tissues.

Effects of intermittent and continuous administration of decoquinate on bovine coccidiosis in male calves.

Male Holstein calves were each inoculated with 350,000 sporulated oocysts of Eimeria bovis. Two calves were given decoquinate (0.5 mg/kg of body weight) continuously in dry feed for 29 days, and 2 calves each were given 0.5, 1, or 1.5 mg of decoquinate/kg on an every 2nd-or 3rd-day schedule for 29 days. Calves given decoquinate continuously did not discharge oocysts but had slightly loose feces. In general, the number of oocysts discharged increased and fecal consistency decreased as the time between feeding of medicated feed increased. Calves given 0.5 or 1.5 mg of decoquinate/kg every 3rd day discharged more oocysts and had more diarrhea than did calves given 1 mg of decoquinate/kg every 3rd day. At postinoculation day 29, calves were euthanatized. At necropsy, intestinal tissues of calves given decoquinate were mostly normal. Apparently, reduced infections along with the elapsed time were sufficient to resolve most intestinal lesions caused by the coccidia. Decoquinate was most effective when fed continuously at 0.5 mg/kg. However, when fed at 1 or 1.5 mg of decoquinate/kg every 2nd day or 1.5 mg of decoquinate/kg every 3rd day, oocyst production was reduced and clinical coccidiosis was prevented.

Preferential grazing by cattle on glyphosate-treated fescue pastures.

Cattle grazing preferences on fescue pastures treated with the herbicide glyphosate at a rate of 2.52 kg/ha by surface application were determined, and the time course of the effect was characterized. An initial grazing preference for treated pasture was observed for the first 5 to 7 days. Over the next 15 days, this preference was lost because of decreasing amounts of herbicide on the herbage and/or desiccation of the herbage.

Effect of decoquinate on the control of coccidiosis in young ruminating calves.

Twenty-five 6-week-old Holstein male calves were each inoculated with 500,000 sporulated oocysts of Eimeria bovis. Two nontreated (control) and 3 treated calves (1.5 mg of decoquinate/kg of body weight in feed) were necropsied 7 days after inoculation. Similar groups of calves were necropsied at 12, 18, 22, and 28 days after inoculation. Treated calves were started on medicated feed 2 days before inoculation or at 7, 12, or 15 days after inoculation or were on continuous medication from the day of inoculation. Control calves were not given medication. Early schizonts were in the small intestines of control calves at 7 days after inoculation, but none was in the treated calves that were started on medicated feed 2 days before inoculation. Schizonts were present in the small intestine of both treated and control calves at 12 days after inoculation. At 18 days after inoculation, control calves had schizonts in the small intestine and gamonts and oocysts in the cecum and large intestines, but treated calves only had schizonts in the small intestine. At 22 days, control calves had schizonts in the small intestine and gamonts and oocysts in the large intestine; treated calves had schizonts in the small intestine. At 28 days, controls still had schizonts in the small intestine and gamonts and oocysts in the cecum and large intestine; the treated calves that had been on continuous medication did not have schizonts, gamonts, or oocysts in the tissues. Decoquinate apparently kills sporozoites or arrests development and release of merozoites from the schizonts when fed at 1.5 mg/kg of body weight in the feed.

Experimental infection of lactating goats with Leptospira interrogans serovars pomona and hardjo.

Pathogenesis of Leptospira interrogans serovars pomona and hardjo was evaluated in 14 lactating goats. Although mild clinical signs of leptospiral infection characterized by pyrexia and reduction in milk yield appeared in some animals, a consistent clinical pattern was not observed in the inoculated animals. The pomona serovar was isolated from the kidney of 1 of the 4 goats inoculated with serovar pomona. The hardjo serovar (strain UI 750) was isolated in the rabbit serum-supplemented bovine albumin polysorbate-80 liquid medium only from the mammary gland of 1 of 4 goats at 13 days after inoculation with serovar hardjo. The positive culture was detected after an 8-month incubation period.

Experimental infection of pregnant and lactating goats with Leptospira interrogans serovars hardjo and szwajizak.

Pathogenesis of 2 Leptospira serovars, hardjo and szwajizak, was studied in pregnant and lactating goats. Although clinical signs of leptospiral infection were minimal, cultural isolations were made from the mammary gland of 2 goats and the kidney of 1 goat inoculated with serovar hardjo (C846). The isolations were made only on solid bovine albumin polysorbate-80 medium supplemented either with rabbit serum or sodium pyruvate. Cultural isolations of serovar szwajizak were made from kidney, liver, brain, urine, and mammary gland samples of 1 goat and the liver and kidney samples of its kids. These isolations were made in only the solid bovine albumin polysorbate-80 medium which had been supplemented with normal goat serum.

Anthelmintic activity of ivermectin against immature gastrointestinal nematodes of sheep.

Twenty-four lambs of mixed breeding with mixed experimental infections of Haemonchus contortus, Ostertagia circumcincta, Trichostrongylus axei, and T colubriformis were allotted to 4 groups. One group (control) was given the vehicle propylene glycol, and the others were given 100, 200, or 300 micrograms of ivermectin/kg of body weight by mouth. Twelve days after treatment, the sheep were necropsied. The compound was greater than 99% effective against immature stages of 4 nematode species at all dosages, except at the 100 micrograms/kg dosage, where efficacy was 96% against H contortus.

A serologic epidemiological study of parainfluenza 1, 2, and 3 viruses in beef cattle and calves in Illinois.

Beef cattle and calves in four Illinois populations were studied. Serum was tested by the hemagglutination-inhibition (HI) test for antibodies to parainfluenza viruses (PIV) 1, 2, and 3. In all but group 3 a low level of antibody to PIV-1 and 2 was demonstrated. The highest prevalence and incidence of HI-antibodies was found for PIV-3, followed by PIV-1. There may have been a cross-reaction between PIV-1 and -3 in Group 1 calves. The low level of HI antibodies to PIV-1 and 2 may have resulted from infections early in life or colostral antibodies that decreased with age.

Control of bovine coccidiosis with monensin: in nonresistant newborn calves.

Newborn Holstein male calves were purchased within 3 days after birth and were removed from the local farms to the Dixon Springs Agricultural Research Center. They were hand-fed for 7 weeks and then weaned to a prepared feed. Eight groups, each of 4 calves, were housed in separate pens. In each of 4 pens (pens 2 to 5), 1 calf was inoculated with sporulated oocysts of Eimeria bovis (and was not medicated); 1 calf was inoculated and given feed with added monensin at the dosage level of 10 g/906 kg of feed; and 2 calves were inoculated and given medicated feed with added monensin at the dosage level of 20 g/906 kg or 30 g/906 kg. In the 4 other pens (6 to 9), the calves were inoculated with E zuernii and otherwise were given feed without or with added monensin as in pens 2 through 5. Another group of 5 calves (all kept in 1 pen), served as noninoculated, nonmedicated controls. At 14 days after inoculations with E bovis, the single calves in each of the 4 pens that were given the nonmedicated feed began to show clinical signs of coccidiosis and discharged increasing numbers of oocysts. The other inoculated calves (given monensin) had fewer clinical signs and discharged fewer oocysts in the feces as the level of medication in the feed increased. The calves inoculated with E zuernii developed only moderately severe infections when compared with those inoculated with E bovis. Inoculated (with E bovis) nonmedicated calves had severe reductions in feed consumption and weight, and 3 of 4 died.(ABSTRACT TRUNCATED AT 250 WORDS)

Anthelmintic efficacy of avermectin B1a and dihydroavermectin B1a against ovine gastrointestinal nematodes in 1977.

In a critical study, 40 female mixed-breed lambs with experimental infections of Cooperia spp, Trichostrongylus colubriformis, Ostertagia circumcincta, T axei, and Haemonchus contortus were allocated to 8 groups in 1977. Groups 1 and 5 served as controls. Groups 2 to 4 were treated orally with avermectin B1a at dosage levels of 25, 50, and 100 micrograms/kg of body weight, respectively. Groups 6 to 8 were given oral dihydroavermectin B1a at dosage levels of 50, 100, and 200 micrograms/kg, respectively. The lambs were euthanatized and necropsied 6 days after treatment. The compounds were greater than 99% effective at all dosage levels.

Evaluation of albendazole in cattle naturally infected with nematodes.

Albendazole (7.5 mg/kg of body weight) was given to 10 calves naturally infected with gastrointestinal nematodes. Ten similar calves served as controls. The compound provided 99% to 100% efficacy in removing Haemonchus placei, Ostertagia ostertagi, Trichostrongylus axei, T colubriformis, Nematodirus spathiger, N helvetianus, N filicollis, Cooperia oncophora, C punctata, and Oesophagostomum radiatum.

Comparative study of vaccines in preventing respiratory disease in beef calves after weaning.

Vaccines against infectious bovine rhinotracheitis (IBR), bovine viral diarrhea (BVD), bovine parainfluenza-3 (PI-3), and bacterin against Pasteurella hemolytica and P. multocida were studied to determine their effectiveness when given 30 days before weaning in preventing respiratory disease in beef calves after weaning. A total of 310 calves, 6 to 8 months old, were divided into 3 groups. Group I consisted of 51 calves vaccinated with a temperature sensitive mutant vaccine intranasally (IBR-PI-3 TSV2). The 56 calves in Group 2 received another intranasal vaccine containing a modified live virus (IBR-PI-3 IP). Calves in both groups received a modified live bovine virus diarrhea (BVD) virus vaccine 30 days before weaning, and a bacteria containing Clostridium chauvei-septicum, Pasteurella hemolytica, and P. multocida. The bacterin was given twice, 2 weeks apart before weaning. The remaining 207 calves were used as unvaccinated controls. All calves were treated at lest once after weaning for clinical respiratory illness. The only virus isolated was PI-3. The serologic response to the viral vaccines was good. There was some doubt as to the effectiveness of the PI-3 component because vaccinated calves were affected by this virus after weaning. Further studies are needed on PI-3 virus vaccine and the most effective vaccination schedule. Vaccination at the time of weaning may have been helpful in the present experiment in preventing clinical disease.

Evaluation of four forms of oxfendazole against nematodes of cattle.

Oxfendazole, methyl [5-(phenylsulfinyl)-1H-benzimidazol-2-yl] carbamate, was evaluated in calves naturally infected with endoparasites. The compound was used as a drench, a paste, a bolus, and as top-dress crumbles at a dosage of 2.5 mg/kg of body weight. The four formulations produced similar effects and were 99% to 100% effective in removing the following adult parasite genera: Haemonchus, Ostertagia, Trichostrongylus. Cooperia, Bunostomum, Oesophagostomum, and Dictyocaulus. Mean efficacy against Trichuris spp varied from 87% to 95%, depending on the formulation used.

Augmentation of hemagglutination-inhibition (HI) antibodies in gilts of breeding age by large dosages of human A/New Jersey/76 influenza vaccine.

Fifteen gilts of breeding age were studied. Four received three 4 ml. doses three weeks apart of an experimental killed swine influenza vaccine containing A/Swine/ill/65 antigen, four received three ml. doses three weeks apart of a human influenza vaccine containing A/New Jersey/76 antigen and three received two doses of human influenza vaccine followed by a 3 ml. third dose of experimental swine influenza vaccine. All except one vaccinate responded to two doses of vaccine by the time of the third dose of vaccine. HI titers were highest four weeks after the third dose of vaccine. Geometric mean titers were highest in animals receiving human influenza vaccine containing A/New Jersey/76. Titer profiles dropped markedly by 60 days after the third vaccination.

Detection of Moraxella bovis antibodies in the SIgA, IgG, and IgM classes of immunoglobulin in bovine lacrimal secretions by an indirect fluorescent antibody test.

The relationship between clinical infectious bovine keratoconjunctivitis (IBK) and Moraxella bovis antibodies was evaluated in a herd of calves during one summer. The detection and the distribution of antibody response in lacrimal secretions of beef calves to natural exposure of M bovis were determined by an indirect fluorescent antibody test. Three classes of immunoglobulins--secretory IgA, IgM, and IgG--were monitored in lacrimal secretions over a 5-month period when IBK was enzootic in the herd. The 3 classes of antibody to M bovis were detected in all but 2 calves at the start of the monitoring, and the highest and most persistent M bovis antibody titers were in the IgG immunoglobulin class, and less so in IgM and secretory IgA classes. The specific antibodies present in the lacrimal secretions did not prevent the development of clinical IBK in the calves.

Haemonchus contortus infections in Targhee and Targhee-Barbados Black-Belly cross lambs.

Targhee and Targhee-Barbados Black-Belly cross lambs that were raised helminth-free were experimentally infected with 10,000 or 25,000 infective larvae of Haemonchus contortus. There were no significant (P = less than 0.05) differences in results of weight gain, packed cell volumes, numbers of eggs per gram of feces, or numbers of helminths between the 2 groups of lambs.