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|Kokzidiose beim Dromedar (Camelus dromedarius)|
|Main title||Kokzidiose beim Dromedar (Camelus dromedarius)|
|Title variations||Coccidiosis in dromedaries (Camelus dromedarius)|
Place of birth: Seelow
|1. Referee||Herr Prof. Dr. Rolf Karl Schuster|
|Further Referee(s)||Herr Prof. Dr. Dr. h. c. mult. Theodor Hiepe
Frau Univ.-Prof. Dr. Johanna Plendl
|Keywords||Camelus, Camels, Dromedaries, Protozoan Infections, Coccidiosis, Eimeria cameli (Eimeria dromedarii, Eimeria rajasthani), Oocysts, Triazines|
|Classification (DDC)||630 Agriculture, Veterinary medicine|
|Summary||Eimeria – infections are protozoan parasitoses that occur worldwide among many domestic and farm animals, thus also among Old World Camels (OWC). The morphology, the endogenous and exogenous development of Eimeriae that are specific for camels as well as the alterations that can be detected histopathologically in such an infection are not comprehensively investigated and the majority of publications on this topic is more than 20 years old. Furthermore, there are no studies on factors associated with Coccidiosis (Eimeriosis) which is the clinically relevant form of an Eimeria infection. At present, the anticoccidial drug toltrazuril (Baycox®) is being used but is not registered for OWC. In addition there is largely a lack of understanding for the pharmacocinetic, tolerance and effectiveness in this genus. It was the goal of this work to collect new information about all of the above questions.
Dromedaries were experimentally infected with E. cameli using different experimental set-ups, such as age, type of housing, infectious dose and medication. The course of the infection was investigated. To describe the endogenous development of E. cameli daily faeces samples were collected and examined for oocysts using a quantitative test [sedimentation]. Trials on the tenacity and observation of sporulation served to collect data on the exogenous development of the parasite. Furthermore, studies on the morphology of sporulated oocysts of this species were conducted. Histopathological examinations on 1,192 intestine sections of 221 OWC were done to describe pathological alterations as well as the location of the developmental stages in the gastrointestinal tract. Together with microbiological data this information was used to conduct a statistical analysis on potential risk factors for clinically relevant coccidiosis. In addition a possible association with other endoparasites was tested. Finally, pro- and metaphylactic treatment with toltrazuril (Baycox®) were conducted on experimentally infected dromedaries.
This work deals with the three species E. cameli, E. dromedarii and E. rajasthani in OWC in Dubai. For E. cameli a prepatent period of 16 - 40 days could be determined by experimental infection as well as a patent period of 12 - 48 days. The shedding curves showed mostly a bimodal distribution which is compatible with an undulating excretion of oocysts. This could be due to two asexual proliferation phases in E. cameli that are staggered in time. It was not possible to identify a clear circadian dynamic in the oocyst excretion. After experimental infection between 20 x 106 and 182 x 106 oocysts were shed. Among all animals the one with the lowest infectious dose and the youngest age shed most occysts. None of the different infectious doses led to a clinically apparent illness compatible with coccidiosis. Repeated blood samples showed that neutrophile granulocytes can be elevated during the prepatent period as a possible consequence of an Eimeria – infection.
At an ambient temperature of 22 - 24°C E. cameli sporulated within 8 - 20 days. E. cameli is very robust towards high temperatures and low relative humidity. Prevalence data from routine faeces samples in the emirate of Dubai were analysed for a period of 4 years, between 2003 – 2006. There was no significant variation over the years. In addition, prevalence from month to month were rather constant with a monthly average of 16.3 %.
The morphological studies were able to describe the fragile and transparent outer veil of E. cameli which was detected for the first time by YAGOUB (1989). The endogenous developmental stages can be found principally in the Lamina propria mucosae of the epithelium of the small intestine. The highest number of parasites can be found in the crypts of jejunum and ileum.
Compared with an infection with E. cameli or small Eimeriae alone a mixed infection with Eimeria species (E. cameli + small Eimeriae) was statistically significantly associated with coccidiosis, the clinically relevant course of an Eimeria infection. It is possible that this risk is elevated further with a concurrent Cl. perfringens infection with irreversible damage in vital organs leading to death.
Medication experiments with toltrazuril (Baycox®) showed that this anticoccidial drug (when given once oral p.i. on different days) was not able to interrupt the life cycle and a patent infection of Eimeriae. Giving the drug three times oral with a dose of each 20 mg/kg body weight with intervals of 5 to 6 days no side effects were observed supporting the notion of good tolerability. The rapid increase of the serum level in the first three days demonstrates its rapid absorption. The decline of the curve after reaching the peak supports the idea that toltrazuril is metabolized and its metabolites are excreted.
Literature studies and the own investigations have shown that Eimeria infections in dromedaries are frequent. However, most infections are mono-infections with just one species which, according to my findings, lead in the most of the cases just to a subclinical course of infection. On the other hand, in dromedaries coccidioses can lead to severe and fatal illness. In front of the background of an increasing concentration of animals in camel farms (with an increased risk for infection due to coprophagia) this illness could gain far greater importance in the near future.
|Number of pages||157 S.|
|FU Department||Department of Veterinary Medicine|
|Year of publication||2009|
|Document type||Doctoral thesis|
|Authors comments||Mensch und Buch Verlag|
|Date of defense||2008-08-26|
|Created at||2009-04-02 : 09:08:31|
|Last changed||2010-02-19 : 11:14:37|