Tissue tropism of Toxoplasma gondii in turkeys (Meleagris gallopavo) after parenteral infection

Turkeys are known to be natural hosts for the zoonotic protozoan parasite Toxoplasma gondii. The objective of the present study was to gain further knowledge of possible predilection sites of T. gondii infection in this species after parenteral application of tachyzoites. A total of 38 turkeys were infected with different doses of T. gondii tachyzoites. Birds were killed either 6 to 8 or 10 to 12 weeks after the experimental infection. Fourteen different tissues per bird were investigated by a nested polymerase chain reaction (PCR) for the presence of the parasites’ DNA. T. gondii DNA was found in any type of tissue analysed; in 86.1 % of all infected birds, at least one sample was tested positive. Over all intravenously infected birds, 15.4 % of all analysed samples contained T. gondii DNA. Most frequently affected tissues were liver (43.3 % positive samples), breast muscle (26.7 % positive samples) and heart (20.0 % positive samples), while the brain was less frequently positive (6.7 %). The number of positive tissues varied from zero to seven tissues per animal with at least one T. gondii-positive edible tissue sample in 80 % of all intravenously infected birds. Still, the results did not indicate defined target tissues or a cyst distribution pattern. Nonetheless, edible organs were most frequently parasitised. The number of positive findings did not differ between the early and the late examination time points. Therefore, a persistence of the tissue stages until the end of the study (12 weeks after infection) is concluded.     

Long-term investigations on Toxoplasma gondii-infected primary chicken macrophages

Toxoplasma (T.) gondii is known to infect various cell types including macrophages. In the present study, we generated monocyte-derived macrophage cultures from chicken blood. By flow cytometrical analysis, 84.5 % of the cultivated cells showed typical macrophage properties. Macrophage cultures were cultivated at either 37 °C or 40 °C, respectively, and were infected 72 to 96 h post isolationem with tachyzoites of the T. gondii type II strain ME49 at a rate of 7.5 tachyzoites per host cell. Light microscopical investigations revealed incorporation of tachyzoites into the macrophages and gradual destruction of the infected macrophage culture. Parasite multiplication was observed by a quantitative real time PCR (qPCR) based on the 529-bp fragment specific for T. gondii. Samples were drawn 1 h post infectionem (p.i.), as well as 12, 24, 36, 48, and 72 h p.i. The parasite replication curve showed a transient decrease of parasite stages 12 h p.i. followed by a tachyzoite multiplication. The comparison of different culture conditions showed a significantly higher replication rate of T. gondii at 37 °C (median value 48 h p.i., 289.2 % of the initial tachyzoite number) compared to cultures incubated at 40 °C (median value 48 h p.i., 73.1 % of the initial tachyzoite number) throughout the observation period (P?<?0.05). In general, replication rates were significantly lower than in a standard VERO cell cultures at 37 °C (P?<?0.05). The observed differences were attributed to the physiological chicken macrophage reaction at 40 °C probably approximating the situation in vivo.     

Single oocyst infection: a simple method for isolation of Eimeria spp. from the mixed field samples

The study described a simple method for single oocyst infection which is usually used to maintain the Eimeria spp. as pure strains in the laboratory and to isolate a single species from the mixed field samples.     

<Emphasis Type="Italic">Fasciola hepatica</Emphasis> alters coagulation parameters in sheep plasma in vivo and in vitro

The blood-sucking activities of the liver fluke, Fasciola hepatica, are likely to cause alterations in coagulation during the course of infection; and the effect of F. hepatica on various coagulation parameters was studied during the course of acute and chronic fasciolosis of sheep over a period of 17 weeks. Whole blood and plasma samples from infected sheep (with 800 metacercariae each) and uninfected controls were collected weekly until 17 weeks post-infection (w.p.i.) and the activated partial thromboplastin time (APTT), prothrombin time (PT) and thrombin time (TT) were determined. Additionally, adult F. hepatica were recovered from bile ducts, incubated for the production of excretory/secretory products (ESP) or homogenised and the effect of fluke products on APTT, PT and TT was determined. Anaemia was evident in infected sheep from 8 w.p.i. until 17 w.p.i. Plasma APTT was accelerated during 8, 9, 12, 14, 16 and 17 w.p.i., while PT was prolonged at 8-11 w.p.i. and TT at 10, 14 and 17 w.p.i. Addition of worm ESP or homogenate to plasma resulted in an enhancement of the intrinsic pathway (APTT) together with a prolongation of the extrinsic and common pathways (PT, TT) of coagulation. It was concluded that F. hepatica contains and releases substances that may contribute to coagulation changes in vivo. Further characterisation of the active substance(s) in vitro revealed heat inactivation, a size >30 kDa and inhibition by the proteinase inhibitors Complete and EDTA for the APTT-accelerating substance(s). The TT-deceleration, in contrast, was increased after heating.     

In vitro development of histotropic larvae of Oesophagostomum dentatum under various conditions of cultivation

We performed a total of 14 trials to evaluate the culture conditions suited best for the in vitro production of fourth-stage larvae (L4) of Oesophagostomum dentatum. Chicken embryo extract was shown to be redundant, whereas pig blood serum, trypticase, liver extract, and yeast extract proved to be important medium ingredients. Development to L4 could be moderately accelerated by increases of temperature (40 °C) and of CO₂ concentration (20% in air), but the total yield of L4 could not be improved. Thus, conditions of 38.5 °C and 10% CO₂ are recommended for routine application. Received: 15 June 1998 / Accepted: 9 July 1998     

Influence of experimental <Emphasis Type="Italic">Eimeria zuernii</Emphasis> infection in calves on electrolyte concentrations,acid–base balance and blood gases

Coccidiosis, often caused by Eimeria zuernii, is an important disease in calf rearing and is clinically mainly associated with diarrhoea (PR Fitzgerald in Adv Vet Sci Comp Med, 24:121–143, 1980). Calves were experimentally infected with E. zuernii oocysts to investigate the effects of artificial E. zuernii coccidiosis on electrolyte concentrations, acid–base balance and blood gases. Therefore, animals were assigned to three groups: group 1 (n = 14) served as uninfected control group, group 2 (n = 11) was infected with 150,000 sporulated E. zuernii oocysts per calf, and group 3 (n = 16) was infected with 250,000 sporulated E. zuernii oocysts per calf. Aberrances which were attributed to coccidiosis were observed in the following parameters: sodium and chloride concentrations, pH (only high-dose infected group 3), base excess, standard bicarbonate, total carbon dioxide and partial pressure of carbon dioxide. Alterations were most pronounced in the high-dose infected group 3. Anion gap and oxygen saturation did not show significant differences between the groups. Due to diarrhoea and malabsorption in coccidiosis-affected calves, there is a distinct loss not only of fluid and blood but also of electrolytes and alkaline buffer substances which provokes the development of an acidosis. This is counteracted by metabolism and respiration but cannot be compensated in severely affected and moribund calves.     

Isospora suis: an experimental model for mammalian intestinal coccidiosis

Piglets experimentally infected with 10,000 oocysts of Isospora suis in three identical trials (n=50) were examined clinically and coproscopically from 5 to 11 days post-infection (d.p.i.), weighed in weekly intervals until the fourth week of life and compared to age-matched asymptomatic controls (n=17). Furthermore, 17 infected piglets were histologically examined on days 5–14 p.i. Infected animals had a significantly lower weight gain than the controls and showed diarrhoea throughout, with maximum prevalence and intensity on 6 d.p.i. Half of the animals had diarrhoea for only 2 days or less. The number of diarrhoea days was negatively correlated with weight gain. Oocyst excretion started on 5 d.p.i. with peak prevalences and declined afterwards; a smaller peak was seen on 10 d.p.i. All animals excreted parasites at least once, and most of them excreted for 5–7 days. Oocyst excretion intensity paralleled the prevalence and ranged from 220 to 251,501 oocysts per gram of faeces (opg). Most samples contained 4×10³ to 4×10⁴ opg. The opg values were negatively correlated with faecal scores (samples with diarrhoea contained less oocysts) of the same day and the previous day. Histologically, necrosis followed by atrophy of the villi was most pronounced in the early stage of infection throughout the jejunum and ileum but declined thereafter. On 14 d.p.i., villous atrophy was still noticeable in the jejunum. Histology is difficult to quantify and requires large animal numbers, although the effects are visible for some time. Weight gain and faecal score can be affected by other factors than parasite infection. From the compiled data, we conclude that the established model is suitable to study piglet isosporosis with oocyst excretion being the most reliable parameter, although individual variations are considerable. A negative correlation between excretion and diarrhoea may be responsible for the difficulties in the detection of the parasite in field samples.     

First detection of Echinococcus granulosus sensu stricto (G1) in dogs in central Sudan

Parasitology Research - Eighty-four stray dogs shot as a part of a governmental rabies control program in two neighboring towns of central Sudan were examined for the presence of Echinococcus spp....