Bovine intestinal cellular responses following primary and challenge infections with Calicophoron microbothrium metacercariae.

This study was carried out to establish whether cattle can develop resistance to re-infection by Calicophoron microbothrium by assessing the response of intestinal mucosal globule leukocytes, eosinophils, mast cells and basophils, and the establishment of the parasite in the host. A total of 24 1-year-old Tuli steers were randomly divided into four groups of six animals each and infected with C. microbothrium metacercariae. On the first day of the study, animals in Groups I and II were immunized with 5000 metacercariae and then challenged with 15,000 metacercariae on Day 150 post-immunization. Animals in Group III were immunized with 15,000 metacercariae at the same time that Groups I and II animals were challenged to act as a positive control group. Animals in Group IV were left uninfected and acted as a negative control group. Three animals from each group were slaughtered on Day 28 post-challenge and the remainder were slaughtered on Day 42 post-challenge. The established amphistomes were recovered and histopathological and cytological examinations were done on the jejunum, duodenum, abomasum and the rumen. The establishment rates of the challenge infection in the immunized and challenged groups were lower and ranged from 0 to 0.2% as compared to 6% from naive animals infected as positive controls. Animals immunized and then challenged with C. microbothrium had significantly higher eosinophil, mast cell and globule leukocytes counts in the intestinal mucosa (P < 0.05) as compared to those of the control group. The study indicates that cattle can develop resistance to C. microbothrium re-infection and that eosinophils and mast cells may be important cells in the rejection of the parasite.

Focal metatarsal sinus tracts in a Weimaraner successfully managed with ciclosporin.

Focal metatarsal sinus tracts ('fistulation') are, to the authors knowledge, reported for the first time in a Weimaraner. The six-year-old, entire male had a five-month history of two symmetrical, well-demarcated sinuses on the plantar aspect of each metatarsus. The area surrounding each pair of sinuses was slightly fluctuant and a serosanguineous discharge could be expressed. Cytological examination of the discharge was characteristic of pyogranulomatous inflammation. Bacterial culture showed the material to be sterile. Examination of a skin biopsy revealed a severe inflammatory reaction involving the dermal collagen, with an infiltrate of neutrophils, macrophages, lymphocytes, plasma cells and multi-nucleated giant cells, with some micro-pustule formation. Treatment with ciclosporin induced total remission. Reduction of the dose of ciclosporin resulted in recurrence of the physical signs with further remission on re-introduction of the original dosage. This is the first report of the use of ciclosporin to control this condition.

Observations on mass production of Calicophoron microbothrium metacercariae from experimentally and naturally infected Bulinus tropicus.

In an attempt to establish an ideal method for mass production of Calicophoron microbothrium metacercariae, a study was carried out to compare the shedding capacities of Bulinus tropicus naturally and experimentally infected with C. microbothrium. A total of 906 F1 B. tropicus between 4 and 5 weeks old were each experimentally infected with two C. microbothrium miracidia and monitored for 12 weeks. The infected snails were fed on dried lettuce and fish flakes and were kept in 1 l plastic aquaria housed in a snail room where temperature, light and humidity were controlled. Seventy-four percent of the experimentally infected snails died during the prepatent period and of the remaining, only 13.2% developed patent infection, while 12.5% were refractory. Snail growth rate was poor and the average shedding rate was 20 cercariae per snail per day. Compared to the experimentally infected snails, 2200 adult B. tropicus, collected from the field and naturally infected with C. microbothrium, yielded high numbers of metacercariae. Eighty-four percent of the snails died within 7 weeks of the study with peak mortality occurring from the 2nd to the 4th week of infection and coinciding with an overall decrease in the number of cercariae shed.

A macro- and light microscopical study of the pathology of Calicophoron microbothrium infection in experimentally infected cattle.

Twelve Tuli weaner steers aged 1 year were randomly subdivided into three groups of four animals and infected with different doses of Calicophoron microbothrium metacercariae. Each animal in Group I received a low dose (LD) of 5 000 metacercariae, Group II a medium dose (MD) of 15 000 metacercariae, Group III a high dose (HD) of 25 000 metacercariae and one additional animal was kept as an uninfected control (C). After infection, one animal from each group was slaughtered on Day 28, 42, 56 and 84 post infection (pi) and samples from the ileum, jejunum, duodenum, abomasum and the rumen were collected for histopathological and cytological examination. On Day 28 pi, the gross pathological lesions observed in the duodenum of the LD and the MD animals were similar and comprised duodenal thickening, corrugation, hyperaemia, petechiation and ulceration. In the HD animal the duodenal lesions were similar but more severe. The abomasal folds were severely oedematous in the MD group and nearly occluded the abomasal lumen. Moderate oedema of the abomasal folds was also present in the LD and HD animals. The gross pathological lesions regressed in all the infected groups with increasing age of infection and had disappeared completely by Day 56 pi. On Day 28 pi the histopathological lesions in the duodenum and jejunum of the LD and MD groups were similar, comprising subtotal villous atrophy, hyperplasia of Brunner's glands and Peyer's patches and moderate infiltration of eosinophils, mast cells and a few globule leukocytes, basophils and lymphocytes in the lamina propria. The HD group had total villous atrophy, severe hyperplasia and cystic dilatation of Brunner's glands, which had expanded to cover the entire submucosa. On Day 42 pi the histopathological lesions were still present in the MD and the HD groups comprising subtotal villous atrophy and hyperplasia of Brunner's glands. Heavy infiltrations of eosinophils, moderate amounts of mast cells and a few basophils, globule leukocytes and lymphocytes were still present in the lamina propria of all three groups. On Day 56 pi, a few glands were still cystic in the MD and the HD groups. Moderate cell infiltrations were still present in the lamina propria of all the three groups and by Day 84 pi complete regeneration had occurred in all animals.

Stromal cells and extracellular matrix components in spontaneous canine transmissible venereal tumour at different stages of growth.

Stromal cells and extracellular matrix (ECM) components are important for tumour cell behaviour. Little is known about the role of stromal cells and ECM components in the progression and regression of spontaneous canine transmissible venereal tumour (CTVT). In this study, the stromal cell type was determined by immunohistochemical labelling with antibodies to desmin, vimentin and alpha-smooth muscle actin (alpha-SMA) during the progressive and regressive stages of spontaneous CTVT. The distribution of ECM components tenascin-C, chondroitin sulphate and versican were determined immunohistochemically, and hyaluronan distribution was determined using a biotinylated protein complex with specific affinity for hyaluronan. Stromal cells of tumours in both the progressive and regressive stage were positive for vimentin and negative for desmin. The number of stromal cells expressing alpha-SMA was significantly higher (P=0.001) in regressing tumours, than progressing tumours. These results suggest that the modulation of stromal cells that occurs during the regression of CTVT is similar to that occurring during wound healing. Tenascin-C was weakly expressed in the stroma of tumours in the progressive stage and in regions of the regressing tumours with tumour infiltrating lymphocytes (TILs), but intensely expressed in the stroma of tumours in late regressive stage. In addition, tenascin-C was also expressed in the cytoplasm of some tumour cells in the late regressive stage. A strong stromal tenascin-C intensity was significantly associated with regressing tumours (P=0.001). Strong stromal hyaluronan intensity and a high proportion of hyaluronan-positive tumour cells were significantly associated with progressing tumours (P=0.001). This suggests that hyaluronan is involved in the growth of the tumour. There was no significant difference in the expression of chondroitin sulphate and versican in progressing and regressing tumours.

The adjustment of curricula in veterinary faculties in sub-Saharan Africa.

A survey was conducted by questionnaire to assess the current undergraduate curricula in the veterinary faculties of sub-Saharan Africa. The survey also examined how such curricula are adjusted for crucial developments in the veterinary field, such as privatisation, decentralisation and globalisation, with the increasing risk of transboundary diseases. The results demonstrate that most of these faculties face serious shortages, both in their budgets and of qualified personnel. Most faculties do not have formal feedback systems to allow former graduates to contribute to periodic reviews of the curricula. Although some north-south and south-south collaboration exists among African veterinary faculties, more intensive regional collaboration at both undergraduate and postgraduate level would allow optimal use of the available funds and human resources. The creation of a regional veterinary council and a committee of deans would be an excellent step forward in ensuring internationalisation and harmonisation of veterinary education and establishing a regional accreditation system.

The effect of treatment with a 1% injectable formulation of moxidectin during the rainy season and at the beginning of the dry season on gastrointestinal nematodes in cattle from communal areas in Zimbabwe.

The effect of 1% moxidectin/cydectin at 0.2 mg/kg live weight on gastrointestinal nematodes and on the growth of calves, weaners and cows was investigated in five communal areas on the highveld of Zimbabwe. Three field experiments were carried out between March 1996 and June 1997. In experiment 1, treatment was administered in all five areas at the end of the rainy season in March 1996, followed by a further treatment at the beginning of the dry season in May/June 1996. In experiment 2, the treatment was administered in three areas at the end of the rainy season in March 1997. In experiment 3, treatment was administcred in one area at the beginning of the dry season in April 1997. Large numbers of eggs were present in the faeces of calves and weaners at the start of experiments 1 and 2. Epg values were lower in cows and in all age categories in experiment 3. There was a statistically significant reduction in epg values in calves, weaners and cows following treatment with a reduction of 90-99% in all cases except in cows in experiment 3, where no meaningful assessment was possible owing to the low egg counts in both the treated and control cows. The dominating larval types in faecal cultures were Cooperia and Haemonchus. Trichostrongylus, Oesophagostomum and Bunostomum were also found. Following treatment, Haemonchus was suppressed far more than Cooperia. This may be related to a longer residual effect against abomasal parasites like Haemonchus in comparison to small intestinal worms like Cooperia. Anthelmintic treatment conferred significant weight gain advantages (p < 0.05) on treated calves. weaners and cows. The weight gains are discussed in relation to disease and nutrition.

A polarized Th1 type immune response to Cowdria ruminantium infection is detected in immune DBA/2 mice.

Immune responses to Cowdria ruminantium, an intracellular organism that causes heartwater in domestic ruminants, were characterized in a DBA/2 mouse model. Immunity induced by infection and treatment was adoptively transferable by splenocytes and could be abrogated by in vivo depletion of T cells but not by inhibition of nitric oxide synthase using NG-monomethyl-L-arginine. IgG2a and IgG2b C. ruminantium-specific responses were detected in immune mice. Culture supernatants of splenocytes from immune DBA/2 mice, which were stimulated with crude C. ruminantium antigens or recombinant major antigenic proteins 1 or 2, contained significant levels of interferon (IFN)-gamma and interleukin (IL)-6, but insignificant levels of IL-1alpha, IL-2, IL-4, IL-5, IL-10, IL-12, tumor necrosis factor-alpha (TNF), and nitric oxide. A similar response was detected during primary infection, although IFN-gamma levels decreased significantly during clinical illness and then increased following natural or antibiotic-aided recovery. These data support the conclusion that protective immunity to C. ruminantium in DBA/2 mice is mediated by T cells and is associated with a polarized T helper 1 type of immune response. This murine model could be utilized to screen for protective C. ruminantium antigens that provoke Th1 type immune responses and for evaluation of these antigens in recombinant vaccines against heartwater.

CD8(+) T cell knockout mice are less susceptible to Cowdria ruminantium infection than athymic, CD4(+) T cell knockout, and normal C57BL/6 mice.

The role of T cells in immunity to Cowdria ruminantium was investigated by studying the responses to infection of normal, athymic, CD4(+) T cell knock out (KO) and CD8(+) T cell KO C57BL/6 mice. Normal C57BL/6 mice could be immunized by infection and treatment, and immunity was adoptively transferable from immune to naive mice by splenocytes. Following infection, athymic mice died sooner than normal mice (P=0.0017), and could not be immunized by infection and treatment. CD4(+) T cell KO mice were as susceptible to infection as normal mice and could be immunized by infection and treatment. In contrast, CD8(+) T cell KO mice were less susceptible than normal and CD4(+) T cell KO mice and 43% self-cured, while those that died did so after a prolonged incubation period. Antibody responses to C. ruminantium were CD4(+) T cell dependent, because responses were detected in immune normal and CD8(+) T cell KO mice but not in immune CD4(+) KO mice (P=0.005). Since CD8(+) T cell KO mice were less susceptible to infection, and since CD4(+) T cell KO mice could be immunized, it can be concluded that immunity to C. ruminantium can be mediated by both CD4(+) and CD8(+) T cells.

Resistance to diminazine aceturate by Trypanosoma congolense from cattle in the Zambezi Valley of Zimbabwe.

The susceptibility of 14 stocks of Trypanosoma congolense, recently isolated from cattle, to therapeutic doses of diminazene aceturate and to isometamidium chloride was assessed in laboratory mice. Eight isolates were readily susceptible to the normal therapeutic dose of diminazene, two were resistant to the drug at 14 mg kg-1, and four were totally resistant at 28 mg kg-1. All the isolates were susceptible to isometamidium chloride at 0.5 mg kg-1. These observations highlight the need for regular evaluation of drugs used in the control of trypanosomosis.

Influence of season and housing on ovarian activity of indigenous goats in Zimbabwe.

Progesterone profiles were monitored in goats housed in single (n = 9) or group (n = 14) pens during winter (JJA) and spring (SON). Normal cycles (n = 97) were < or = 30 days. Extended cycles (n = 45) were > 30 days and, except for one cycle with a persistent corpus luteum, had periovulatory periods of 10 to 20 days (n = 29) or averaging 65.1 days in length (n = 15), mostly characterised by recurrent oestrus and/or occasional transient rises in progesterone. The proportion of normal cycles occurring in winter was 87.5% (28/32) and 77.7% (42/54) for goats in single and group pens respectively, falling to 62.5% (15/24) and 37.5% (12/32) respectively in spring. The distribution of normal vs extended cycles according to season was significant (P < 0.05, single; P < 0.001 group pens). Goats housed communally experienced a greater fall in the percentage of normal cycles in spring, possibly due to increased stress associated with group feeding. Within each season, however, housing per se did not influence the distribution of normal vs extended cycles. For normal cycles, Harvey's Analysis of Variance showed that season was significantly associated with length of the periovulatory period (3.99 days (JJA) vs 5.79 days (SON); P < 0.001), oestrus detection rate (87% (JJA) vs 55% (SON); P < 0.01) and oestrus duration (1.94 days (JJA) vs 1.13 days (SON); P < 0.05). In contrast, luteal phase length was not affected by season, but was significantly associated with housing (16.93 days (single pens) vs 18.32 days (group pens); P < 0.01). The reduction in ovarian activity observed in spring may reflect a seasonal reduction in fertility, possibly linked with increasing temperature and photoperiod.

The effect of diet on aflatoxin B1 binding to hepatic macromolecules in rats.

Fischer 344 rats were fed a low-fat high carbohydrate diet (HC), an isocaloric fat-containing diet (IC), a hypercaloric fat-containing diet (HF) or rat chow. Covalent binding of AFB1 to liver DNA, RNA and total proteins was investigated in a 24 hour period following administration of a single intraperitoneal dose of AFB1 (1 mg/kg body weight). AFB1 binding to nucleic acids was greatest in the HC and was generally significantly lower (p < 0.05) in the HF, IC and rats fed chow. The results suggest that fat decreases hepatic macromolecular adduct formation by inhibiting activation of AFB1 to the epoxide or by enhancing the activity of detoxification pathways.

Plasma progesterone concentrations during pregnancy and pseudopregnancy and onset of ovarian activity post partum in indigenous goats in Zimbabwe.

Eight pregnant does were housed individually and fed a hay and concentrate diet throughout pregnancy and lactation. The mean gestation period was 146.7 +/- 3.0 days, with a twinning rate of 75 per cent. Mean body condition scores improved from 2.4 +/- 0.2 to 2.8 +/- 0.2 over the first 80 days of gestation and were maintained at 2.8 until 45 days before kidding. From then until kidding, mean scores fell to 2.2 +/- 0.2. Plasma progesterone concentrations during pregnancy rose significantly from 3.91 +/- 0.51 ng/ml on day 40 to 5.96 +/- 0.51 ng/ml on day 60 (P < 0.05) and remained high until 5 days before kidding. Three pseudopregnant does had similar progesterone profiles to pregnant does over the first 80 days, but the rise around day 35 to 40 was not significant and progesterone concentrations returned gradually to basal levels after day 100. The same 8 does, together with an additional 4 does which had been brought inside 60 to 70 days before kidding, were used to study onset of ovarian activity post partum. The twinning percentage was 83 per cent. Mean body condition score at parturition was 2.2 +/- 0.1. By day 35 post partum, mean condition scores had fallen to 1.9 +/- 0.1, and mean weights from 36.9 +/- 1.9 kg at kidding to 32.1 +/- 2.0 kg. Ovarian cyclicity was resumed just before mean scores and weights started to improve. The mean interval from kidding to onset of oestrous cycles was 97.3 +/- 9.5 days. This coincided with mean time to weaning which was 99.5 +/- 5.5 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Mycoplasma ovipneumoniae infection in Zimbabwean goats and sheep.

The prevalence of Mycoplasma ovipneumoniae (MO) in three Communal Lands flocks of goats on the outskirts of Harare is described. In a single sampling of nasal swabs from 172 randomly selected, apparently healthy goats, 112 animals were identified as carriers of MO. The three flocks had a history of occasional deaths, following chronic and subacute pneumonia associated with isolation of MO as the only identifiable pathogen. Attempts to induce clinical pneumonia in groups of 6 to 8-week-old kids and lambs with local isolates of MO were not successful. However, MO was consistently cultured from the trachea, lungs, lymph node and thymus of some test animals. Cuffing interstitial pneumonia was also observed in these animals. Infection of the thymus occurred; this has not previously been reported with any Mycoplasma sp. The animals did not produce detectable serum antibodies to MO nor were they reactive to MO antigen in a tuberculin-type hypersensitivity test. The possibility that a state of immunotolerance may have been responsible for failure to develop clinical pneumonia is discussed.

Idiopathic septic gonitis in five Holstein-Friesian heifers.

Five cases of gonitis in young cows are reported. In all cases lameness was severe with no weight bearing on the affected limbs. The joints were swollen. No organisms were isolated from the fluids aspirated from the joints but cytological examination showed large numbers of neutrophils, and biochemical analysis showed increases in the activities of aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase and lactate dehydrogenase.

Schistosomal lesions in the bovine uterus.

Inspection of bovine female genitalia at a major abattoir in north-eastern Zimbabwe showed schistosome-induced granulomas in uterine walls. Thirty-six non-pregnant and 7 pregnant uteri of 3441 examined, had lesions either in the mid-dorsal aspect of the uterine body or in the horns. The reproductive history of the cows was not known but the 7 pregnancies appeared normal. Lesions were most severe in the myometrium and consisted of rings of multinucleated giant cells and macrophages occurring around eggs and masses of eosinophils on the outside. The parasite is presumed to be Schistosoma mattheei.