The survival in sheep and infectivity to dogs of Taenia hydatigena and T. ovis in sheep

Lambs were reared from birth to 3 months of age on pasture contaminated with the eggs of either Taenia hydatigena or Taenia ovis. They were necropsied at 3, 6, 9 or 12 months. Almost all larvae that were viable at 3 months continued to survive throughout the experiment. Larvae of T. hydatigena were infective to dogs at 3 months, whereas those of T. ovis required more than 3 months to reach the infective stage.     

The serological response of dogs to Taenia ovis

The effect of 4-weekly anthelmintic dosing and other treatment regimes on the serological response of dogs to Taenia ovis was examined. Most dogs which were frequently fed infected meat and dosed with a cestocidal anthelmintic at 4-week intervals eventually showed a positive ELISA absorbance. The absence of dosing, or intermittent dosing, of repeatedly infected dogs raised ELISA absorbances to very high levels in most dogs and these absorbances took an increasingly longer time to fall after each new infection. The feeding of large numbers of frozen, dead cysts to sensitised dogs raised absorbance levels. The serological test for T. ovis infections in dogs does not detect false positives. Positive tests result from the dog being exposed to T. ovis scolex secretory antigen.     

The serological response of dogs to Taenia ovis

The effect of 4-weekly anthelmintic dosing and other treatment regimes on the serological response of dogs to Taenia ovis was examined. Most dogs which were frequently fed infected meat and dosed with a cestocidal anthelmintic at 4-week intervals eventually showed a positive ELISA absorbance. The absence of dosing, or intermittent dosing, of repeatedly infected dogs raised ELISA absorbances to very high levels in most dogs and these absorbances took an increasingly longer time to fall after each new infection. The feeding of large numbers of frozen, dead cysts to sensitised dogs raised absorbance levels. The serological test for T. ovis infections in dogs does not detect false postives. Positive tests result from the dog being exposed to T. ovis scolex secretory antigen.     

Muscular cysticercosis from Taenia ovis in feedlot lambs.

From a Colorado enterprise annually fattening about 50,000 lambs, 3,664 animals were examined for muscular cysticercosis. Of the total number, 406 (11.1%) were parasitized, wheras an estimated 0.1% of Colorado lamb carcasses are infected. Of the infected lambs, 60% had cardiac lesions. Two types of cysticerci-viable and degenerated-were found. The lambs probably acquired infection from grazing summer ranges and pastures where coyotes or dogs infected with Taenia ovis contaminated the forage.     

Oncospheres of Taenia solium develop into cysticerci in normal mice

In vitro-hatched oncospheres of Taenia solium, prepared by the sodium hypochlorite method and adjusted to approximately 5 x 10(2)/2ml phosphate buffer saline, were injected intramuscularly or intravenously into normal Balb/c mice. When these mice were sacrificed 2 months later, all cysticerci were exclusively recovered in the lungs from the mice with intravenous inoculation, but not with intramuscular injection. A high infection rate of 76% was obtained and a total of 45 cysticerci were collected from 50 mice. Thirty-five cysticerci were mature and with normal appearance but the rest were either with abnormal appearance (4) or degenerated (6). These findings give strong evidence that T. solium oncospheres may migrate to the normal mouse lung through venous circulation and develop in this organ.     

The behaviour of sheep with sheep scab, Psoroptes ovis infestation.

Methods of behavioural data collection as applied to the study of sheep scab are described. The behaviour of a number of marked animals within an affected flock was recorded using an event recorder. Focal sampled data were analysed for duration and frequency of the observed behaviours. In addition, the flock was observed at intervals and the instantaneous behaviour of each animal recorded. These data were compared with similar observational data from the same flock recorded at intervals during post-treatment recovery. Sheep scab resulted in pathological behaviours of rubbing, scratching and biting at the lesion, and these resulted in interruption of the normal behaviours, grazing, cudding and idling, but did not result in reduced levels of these behaviours. Infested sheep showed stereotypic mouthing behaviour, initiated by rubbing or scratching, or in some cases without any external stimulus. No stereotypic behaviour was seen in animals after treatment. The implications of the behavioural data for the welfare of the sheep is discussed.     

The importance of the New Zealand campaign against Echinococcus granulosus and Taenia hydatigena on the prevalence of Taenia ovis

Extract

An important aspect of the campaign in New Zealand directed against Echinococcus granulosus and Taenia hydatigena is its possible effect on the prevalence of Taenia ovis. The burying of offal to eliminate E. granulosus and T. hydatigena is recommended as being preferable to cooking it and feeding it to dogs. The drastic reduction in the number of European rabbits (Oryctolagus cuniculus) in many districts has also virtually eliminated an important dog-food. Consequently, in addition to commercial products, many farmers are relying on more sheep carcass-meat than previously as a source of dog-food. Other things being equal, conditions would seem ideal for an increase in the prevalence of. T. ovis. This is particularly significant to New Zealand which depends so much on a meat export trade. Damage to this on account of T. ovis could in turn pre- judice a campaign directed against E. granulosus and T. hydatigena.     

The effects of Eperythrozoon ovis in sheep

Infection of adult sheep with a single strain of Eperythrozoon ovis led to three different situations. First, the animal resisted the organism and no haematological changes occurred. Second, the host developed a controllable parasitaemia in which erythrocyte values fell shortly after peak parasitaemia and then returned to normal. Third, the host failed to control the parasitaemia and chronic low grade anaemia developed. Dexamethasone sometimes caused a resurgence of parasitaemia in sheep.     

Performance of the ELISA test for swine cysticercosis using antigens of Taenia solium and Taenia crassiceps cysticerci

Studies were conducted to evaluate antigens of Taenia solium (Tso) and Taenia crassiceps (Tcra) cysticerci in the ELISA test for the diagnosis of swine cysticercosis. The samples analyzed were cysticercosis positive and negative control sera and heterologous sera. Four antigens were assayed: vesicular fluid (VF) and crude (T) Tcra and scolex (S) and crude (T) Tso. All antigens showed good performance, but VF-Tcra was the best followed by T-Tcra. Sensitivity rates of ELISA were respectively, in 2nd and 3rd standard deviation cut-offs, 96.0 and 80.0% for the VF antigen and specificity of 97.5 and 100.0%. Cross-reactivity was verified only for hidatidosis and ascaridiosis. Due to the high performance observed, the ELISA test using Tcra antigens should be recommended for the diagnosis of swine cysticercosis.