Influence of Calicophoron microbothrium amphistomosis on the biochemical and blood cell counts of cattle.

Sixteen Tuli steers aged 1 year were subdivided into four equal groups (I-IV) and infected with Calicophoron microbothrium metacercariae. Group I received a low dose (LD) of 5000 metacercariae, group II a medium dose (MD) of 15,000 metacercariae, group III a high dose (HD) of 25,000 metacercariae while group IV was the non-infected control (C) group. The experimental animals were monitored daily for clinical signs while ethylene diamine tetraacetic acid (EDTA) blood and serum samples were collected every 7 days until day 28 post-infection, when sample collection was terminated. Samples were processed for full blood count, eosinophils and blood biochemical values for calcium, magnesium, phosphorus, total protein and albumin. Moderate to severe diarrhoea developed in the MD and HD groups at day 21 post-infection. The diarrhoea coincided with a significant decrease (P < 0.05) in total plasma protein, calcium and phosphorus levels, particularly in the MD group. Similarly, a significant decrease (P < 0.05) in the packed cell volume (PCV), the haemoglobin (Hb) and red blood cell (RBC) levels occurred in the MD and HD groups from day 21 post-infection, while a significant increase (P < 0.05) in the circulating eosinophils occurred between 7 and 21 days post-infection in the LD and the HD groups.

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.

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.

Kalanchoe lanceolata poisoning in Brahman cattle in Zimbabwe: the first field outbreak.

Field outbreaks of Kalanchoe lanceolata poisoning in cattle on a commercial farm in Zimbabwe are reported. The clinical signs and pathological lesions observed in field cases resembled those reproduced in an experimental cow and were consistent with acute cardiac glycoside poisoning.