Seroprevalence rates of Toxoplasma gondii anti-antibodies in adult goats and sheep from different parts of Zimbabwe were determined. A total of 225 (67.9 %) of the 335 serum samples tested were positive for anti-T. gondii IgG antibodies with the indirect fluorescent antibody test. There were differences in antibody seroprevalences among communal land goats from the different agro-ecological zones (Natural regions IIb and III: 80 and 96.7 %, respectively; Natural region IV: 65.9 %; Natural region V: 45 %; and Natural region III had a significantly higher seroprevalence than IV and V. The highest seroprevalences found in Natural regions II b and III are likely to be linked to the existence of more households and hence the possibility of a higher concentration of domestic cats that increases the chances of environmental contamination with their faeces harbouring T. gondii oocysts. The seroprevalence rate in sheep from a large commercial farm (10 %) was significantly lower than that of sheep reared under the communal grazing system (80 %). Overall, significantly higher proportions of seropositive animals had antibody titres of 1:50 (34.2 % of 225) and 1:100 (44 % of 225) as compared to the 9.8 % and 12 % with antibody titres of 1:200 and 1:400, respectively.

Seroprevalence rates of Toxoplasma gondii anti-antibodies in adult goats and sheep from different parts of Zimbabwe were determined. A total of 225 (67.9 %) of the 335 serum samples tested were positive for anti-T. gondii IgG antibodies with the indirect fluorescent antibody test. There were differences in antibody seroprevalences among communal land goats from the different agro-ecological zones (Natural regions IIb and III: 80 and 96.7 %, respectively; Natural region IV: 65.9 %; Natural region V: 45 %; and Natural region III had a significantly higher seroprevalence than IV and V. The highest seroprevalences found in Natural regions II b and III are likely to be linked to the existence of more households and hence the possibility of a higher concentration of domestic cats that increases the chances of environmental contamination with their faeces harbouring T. gondii oocysts. The seroprevalence rate in sheep from a large commercial farm (10 %) was significantly lower than that of sheep reared under the communal grazing system (80 %). Overall, significantly higher proportions of seropositive animals had antibody titres of 1:50 (34.2 % of 225) and 1:100 (44 % of 225) as compared to the 9.8 % and 12 % with antibody titres of 1:200 and > 1:400, respectively.

Ticks were collected at approximately bi-monthly intervals between June 1996 and June 1997 from crested francolins, Francolinus sephaena, and from the vegetation on a mixed cattle and wildlife farm in Limpopo Province, South Africa. The birds were infested with the immature stages of 13 tick species, of which Amblyomma hebraeum, Amblyomma marmoreum and Hyalomma marginatumrufipes were the most numerous and prevalent. Ten ixodid tick species were collected from the vegetation, of which the immature stages of Rhipicephalus appendiculatus, Rhipicephalus (Boophilus) decoloratus and Rhipicephalus evertsi evertsi were the most numerous. No adult ticks were collected from the birds and only two from the vegetation. The restricted home range of crested francolins implies that they could serve as a source of tick infestation only for other animals within the same habitat as the birds.

Ticks were collected at approximately bi-monthly intervals between June 1996 and June 1997 from crested francolins, Francolinus sephaena, and from the vegetation on a mixed cattle and wildlife farm in Limpopo Province, South Africa. The birds were infested with the immature stages of 13 tick species, of which Amblyomma hebraeum, Amblyomma marmoreum and Hyalomma marginatumrufipes were the most numerous and prevalent. Ten ixodid tick species were collected from the vegetation, of which the immature stages of Rhipicephalus appendiculatus, Rhipicephalus (Boophilus) decoloratus and Rhipicephalus evertsi evertsi were the most numerous. No adult ticks were collected from the birds and only two from the vegetation. The restricted home range of crested francolins implies that they could serve as a source of tick infestation only for other animals within the same habitat as the birds.

Five species of ixodid ticks were found in a cross-sectional survey in which 200 sheep were examined for ticks in River Nile Province, Sudan. Hyalomma anatolicum anatolicum was the predominant species (73.6 %), whereas ticks belonging to the Rhipicephalus sanguineus group (14.7 %), Rhipicephalus evertsi evertsi (9.1 %), Rhipicephalus simus (2 %) and Hyalomma dromedarii (0.5 %) were also found. The mean tick load was 11.2 per animal. In a subsequent longitudinal survey ticks were collected on a monthly basis from eight sentinel sheep that were introduced into the area. It was found that H. a. anatolicum almost disappeared during the hot period between April and August, whereas it's highest numbers were present in winter between November and February. It is concluded that there is only one generation of H. a. anatolicum per year, which may explain the yearround appearance of clinical cases of malignant ovine theileriosis indicating endemic instability of this disease in River Nile Province.

Five species of ixodid ticks were found in a cross-sectional survey in which 200 sheep were examined for ticks in River Nile Province, Sudan. Hyalomma anatolicum anatolicum was the predominant species (73.6 %), whereas ticks belonging to the Rhipicephalus sanguineus group (14.7 %), Rhipicephalus evertsi evertsi (9.1 %), Rhipicephalus simus (2 %) and Hyalomma dromedarii (0.5 %) were also found. The mean tick load was 11.2 per animal. In a subsequent longitudinal survey ticks were collected on a monthly basis from eight sentinel sheep that were introduced into the area. It was found that H. a. anatolicum almost disappeared during the hot period between April and August, whereas it's highest numbers were present in winter between November and February. It is concluded that there is only one generation of H. a. anatolicum per year, which may explain the yearround appearance of clinical cases of malignant ovine theileriosis indicating endemic instability of this disease in River Nile Province.

Aqueous decoctions obtained from the galls of Guiera senegalensis were screened to determine their phytochemical composition and in vitro antiviral activity against fowlpox virus. In addition, we wanted to investigate the toxic effects, if any, of crude extracts in chickens. Steroids as well as cardiac glycosides not previously reported, an alkaloid, polyphenols and saponins were detected in the various fractions of organic solvents used for extracting the decoctions. Antiviral activity was determined by cytopathic effect inhibition assay in primary chicken embryo skin cells. The 50 % inhibitory concentration (EC50) was shown to be 15.6 g/ml. Toxicity for cells was established by determining the 50 % cytotoxic concentration (CCy50). A value of 90 g/ml and a selectivity index (CCy50/EC50) of 5.8 were obtained. In vivo studies of toxicity were performed in chickens that were dosed orally with decoctions of several concentrations for 2 weeks and then monitored for 3 months. No significant changes in several blood chemical parameters were obtained, except for a significant decline in SGOT levels in birds dosed with 100 mg/kg. These levels were nevertheless within the accepted normal range. The findings suggest that aqueous decoctions of galls from G. senegalensis are non-toxic for chickens when administered orally, even at a daily dose of 100 mg/kg for 14 days.

Aqueous decoctions obtained from the galls of Guiera senegalensis were screened to determine their phytochemical composition and in vitro antiviral activity against fowlpox virus. In addition, we wanted to investigate the toxic effects, if any, of crude extracts in chickens. Steroids as well as cardiac glycosides not previously reported, an alkaloid, polyphenols and saponins were detected in the various fractions of organic solvents used for extracting the decoctions. Antiviral activity was determined by cytopathic effect inhibition assay in primary chicken embryo skin cells. The 50 % inhibitory concentration (EC50) was shown to be 15.6 µg/ml. Toxicity for cells was established by determining the 50 % cytotoxic concentration (CCy50). A value of 90 µg/ml and a selectivity index (CCy50/EC50) of 5.8 were obtained. In vivo studies of toxicity were performed in chickens that were dosed orally with decoctions of several concentrations for 2 weeks and then monitored for 3 months. No significant changes in several blood chemical parameters were obtained, except for a significant decline in SGOT levels in birds dosed with 100 mg/kg. These levels were nevertheless within the accepted normal range. The findings suggest that aqueous decoctions of galls from G. senegalensis are non-toxic for chickens when administered orally, even at a daily dose of 100 mg/kg for 14 days.

A total of 17 commercially reared ostriches (Struthio camelus) from Msengi farm, Chinhoyi, Zimbabwe, observed with swollen eyes, severe conjunctivitis and constant lacrimation accompanied by a purulent exudate, were restrained for further clinical examination. Some of the birds were semi-blind with severe loss of body condition. When examined, tiny organisms were observed attached to the nictitating membranes and the conjuctival sacs of both eyes. The organisms were identified as Philophthalmus gralli, the "oriental eye-fluke" and Melanoides tuberculata, a prosobranch snail, was confirmed as the intermediate host through natural and experimental infection. To the best of our knowledge this is the first record of the oriental eye-fluke infection in birds in Zimbabwe and Africa and extends its known geographical range.

A total of 17 commercially reared ostriches (Struthio camelus) from Msengi farm, Chinhoyi, Zimbabwe, observed with swollen eyes, severe conjunctivitis and constant lacrimation accompanied by a purulent exudate, were restrained for further clinical examination. Some of the birds were semi-blind with severe loss of body condition. When examined, tiny organisms were observed attached to the nictitating membranes and the conjuctival sacs of both eyes. The organisms were identified as Philophthalmus gralli, the "oriental eye-fluke" and Melanoides tuberculata, a prosobranch snail, was confirmed as the intermediate host through natural and experimental infection. To the best of our knowledge this is the first record of the oriental eye-fluke infection in birds in Zimbabwe and Africa and extends its known geographical range.

Ingestion of the plant Nolletia gariepina was confirmed as the cause of acute mortalities in cattle in the Kuruman area of the Northern Cape Province of South Africa. The aim of this trial was to investigate the toxic effects of this plant with respect to clinical signs, pathophysiology and pathology using the sheep as a model. At dosages of 1.5 g dried, milled plant material/kg body mass there were no detectable abnormal findings, while at dosages of 2.8-3.0 g/kg most of the animals died acutely. In subacutely affected sheep, depression, inappetance, teeth grinding, tachycardia, weak ruminal movements and recumbency were noticed. The most prominent pathophysiological changes observed, included a sharp rise in non-protein nitrogen substances in the plasma, remarkable decline in glomerular filtration rate, increase in sodium and potassium excretion, and a rise in urine gamma glutamyltransferase activity. Macroscopically a severe nephrosis was present in all the animals. The most important findings detected histologically were necrosis of the proximal convoluted tubular epithelium and large numbers of protein casts in the lumens.

Ingestion of the plant Nolletia gariepina was confirmed as the cause of acute mortalities in cattle in the Kuruman area of the Northern Cape Province of South Africa. The aim of this trial was to investigate the toxic effects of this plant with respect to clinical signs, pathophysiology and pathology using the sheep as a model. At dosages of 1.5 g dried, milled plant material/kg body mass there were no detectable abnormal findings, while at dosages of 2.8-3.0 g/kg most of the animals died acutely. In subacutely affected sheep, depression, inappetance, teeth grinding, tachycardia, weak ruminal movements and recumbency were noticed. The most prominent pathophysiological changes observed, included a sharp rise in non-protein nitrogen substances in the plasma, remarkable decline in glomerular filtration rate, increase in sodium and potassium excretion, and a rise in urine gamma glutamyltransferase activity. Macroscopically a severe nephrosis was present in all the animals. The most important findings detected histologically were necrosis of the proximal convoluted tubular epithelium and large numbers of protein casts in the lumens.

A single-tube duplex nested polymerase chain reaction (sdn-PCR) was developed for the detection of and discrimination between ovine herpesvirus-2 (OvHV-2) and alcelaphine herpesvirus-1 (AlHV-1). These viruses respectively cause sheep- and wildebeest-associated malignant catarrhal fever (SAMCF and WA-MCF). In the first step of the sdn-PCR, two primers with high annealing temperatures based on conserved regions of the tegument genes were used for DNA amplification. In the second step, two primer sets based on variable regions of the respective OvHV-2 and AlHV-1 genes and with annealing temperatures 11 C below the primers used in the first step, were used. Internal regions of different sizes from amplicons produced in the first step were amplified. This single-tube test obviates the need for two separate assays to detect both viral types, thereby reducing time, labour and cost.

A single-tube duplex nested polymerase chain reaction (sdn-PCR) was developed for the detection of and discrimination between ovine herpesvirus-2 (OvHV-2) and alcelaphine herpesvirus-1 (AlHV-1). These viruses respectively cause sheep- and wildebeest-associated malignant catarrhal fever (SAMCF and WA-MCF). In the first step of the sdn-PCR, two primers with high annealing temperatures based on conserved regions of the tegument genes were used for DNA amplification. In the second step, two primer sets based on variable regions of the respective OvHV-2 and AlHV-1 genes and with annealing temperatures > 11 °C below the primers used in the first step, were used. Internal regions of different sizes from amplicons produced in the first step were amplified. This single-tube test obviates the need for two separate assays to detect both viral types, thereby reducing time, labour and cost.

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.

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.

Resistance to trypanocidal drugs has been detected in various African countries and is a serious impediment to the control of livestock trypanosomosis. To determine whether drug resistant trypanosome strains are present in the Zambzia Province of Mozambique a study was initiated. To assess the effect of the farming system and the drug-use regimen on the development of drug resistance, trypanosome isolates were collected from cattle from subsistence and commercial livestock production systems. The susceptibility of seven isolates against isometamidium chloride, diminazene aceturate and homidium chloride was tested in mice using a multiple-dose test. In four of the seven isolates high levels of drug resistance to diminazene aceturate and isometamidium chloride were detected. In most cases the observed levels of drug resistance correlated with the drug-use practices in the particular livestock production system.

Resistance to trypanocidal drugs has been detected in various African countries and is a serious impediment to the control of livestock trypanosomosis. To determine whether drug resistant trypanosome strains are present in the Zambézia Province of Mozambique a study was initiated. To assess the effect of the farming system and the drug-use regimen on the development of drug resistance, trypanosome isolates were collected from cattle from subsistence and commercial livestock production systems. The susceptibility of seven isolates against isometamidium chloride, diminazene aceturate and homidium chloride was tested in mice using a multiple-dose test. In four of the seven isolates high levels of drug resistance to diminazene aceturate and isometamidium chloride were detected. In most cases the observed levels of drug resistance correlated with the drug-use practices in the particular livestock production system.

Theileria parva-nave Friesian (Bos taurus), Boran (Bos indicus) and Maasai Zebu steers (B. indicus) were infected with a T. parva sporozoite stabilate dose which had previously been shown to induce an estimated 50 % mortality rate in Boran cattle. All the cattle developed patent infections with no significant differences in the length of the prepatent period to development of macroschizonts (P 0.05) between the three groups. Clinical theileriosis occurred in all eight the Friesians (100 %), five out of nine Borans (55.6 %) and two out of five Zebus (40 %). Three of the Friesians (37.5 %), and two of the Borans (22.2 %) died of theileriosis. The different cattle types were equally susceptible to the infective dose used as indicated by the length of the prepatent periods, but there was a marked difference in their development of clinical theileriosis. The gradation in resistance to disease confirms the findings of earlier less critical studies and identifies these cattle breeds as suitable for investigations into the mechanisms of resistance to theileriosis.

Theileria parva-naïve Friesian (Bos taurus), Boran (Bos indicus) and Maasai Zebu steers (B. indicus) were infected with a T. parva sporozoite stabilate dose which had previously been shown to induce an estimated 50 % mortality rate in Boran cattle. All the cattle developed patent infections with no significant differences in the length of the prepatent period to development of macroschizonts (P > 0.05) between the three groups. Clinical theileriosis occurred in all eight the Friesians (100 %), five out of nine Borans (55.6 %) and two out of five Zebus (40 %). Three of the Friesians (37.5 %), and two of the Borans (22.2 %) died of theileriosis. The different cattle types were equally susceptible to the infective dose used as indicated by the length of the prepatent periods, but there was a marked difference in their development of clinical theileriosis. The gradation in resistance to disease confirms the findings of earlier less critical studies and identifies these cattle breeds as suitable for investigations into the mechanisms of resistance to theileriosis.