Research Group 3: Wildlife diseases

Research field: Parasitology/Ornithology

Head: Dr. O. Krone

The main aim of the parasitological research are parasite-host-relations of carnivourous animals. The parasite fauna as well as the significance of parasites of endangered wild animal species on individual and population scale are examined. In an interdisziplinary aproach covering the causes of death, diseases, and environmental toxins the hypothesis "a parasitosis is a multifactorial disease" will be reviewed. To understand the very complex ecological links between the environment, the host, and the parasite unknown life-cycles of parasites and their range within their host population will be studied.

In cooperation with other research groups and in interdisziplinary projects routine examinations are performed to investigate the parasite burden.

A new research focus is the investigation of the speciation of endoparasites using molecular methods.

1. Diseases and causes of death in large bird

-Mortality factors of white-tailed sea eagles

Diseases and causes of death in white-tailed sea eagles (Haliaeetus albicilla) are examined in cooperation with several veterinary disciplines (pathology, parasitology, bacteriology, virology), governmental nature conservation agencies, eagle protection groups, and ornithological stations. Remarkable are the high numbers of deaths caused by anthropogenic factors. The most important mortality factors are lead intoxication due to ingestion of lead particles and collisions with trains. Among the “natural” causes of death intraspecific conflicts (territorial fights) and infections are predominant (Krone et al. 2002). Lesions of the liver, bile ducts and gall bladder were at first attributed to infections with the liver fluke (Metorchis bilis) therefore the biology (life-cycle) of this parasite was investigated (Krone and Schuster 2002). Based on increasing findings of lead particles in the stomach of the white-tailed sea eagles it tuned out that the liver lesions were mainly caused by lead intoxications. A study together with the Research Institute of Wildlife Ecology, Vienna revealed lead intoxication to be responsible for the death in 1/3 of the sea eagles found dead (Kenntner et al. 2001). In contrast to the lead intoxications pesticides play a minor role nowadays (Kenntner et al. 2003). New threats such as collisions with wind power plants may become an increasing importance (Krone and Scharnweber 2003). Investigations on the mortality factors of white-tailed sea eagles from Greenland (Krone et al. 2004) and Finland (Krone et al. 2006) point to the significance of anthropogenic caused deaths, especially lead intoxications in the eagles.

A current project on the causes of death includes sea eagles equipped with satellite transmitters to estimate the importance of the mortality factors on population level. The first results of this project using GPS-devices can be found here: (more informations here)

 
White-tailed sea eagle

-Development cycle of the liver fluke (Metorchis sp.) from the white-tailed sea eagle (Haliaeetus albicilla)    Abstract

Trematodes (Metorchis sp.) are routinely found in the bile ducts and gall bladder of white-tailed sea eagles. Pathologic alterations caused by the fluke contain irritation of the epithelium layer, cholangiectasis, and blockage of the bile ducts leading to back flow of bile acid into the liver. In few cases this trematode caused the death of its host. The life-cycle partly established in the laboratory should reveal the intermediate hosts involved in the development of the parasite, and answer the questions how do the development stages look like, how long do they need to maturate, and if sensory organs of the intermediate hosts are affected.

The adult fluke lives in the white-tailed sea eagle, the eggs of the parasite leave the host together with the faeces and needs to fall into fresh water, where they are ingested by water snails (Bithynia sp.). Within the snail the parasite multiplys. Later the parasite leaves the snail searching for the next intermediate host a fresh water fish (Cyprinidae) which will be penetrated by the parasite. When the fish becomes the prey to a white-tailed sea eagle the life-cycle of the parasite is completed.

-Phylogeny of endoparasites from birds of prey

Birds of prey host a wide variety of endoparasites. Nematodes from different species can be found mainly in the digestive and respiratory system. In the epithelium cells of the small intestine birds of prey often harbour Sarcocystis oocysts, a cyst-forming coccidia with an obligate heteroxenous life cycle. Intermediate hosts are usually small birds or mammals.

In our project molecular data are used to construct phylogenetic trees in these two groups of endoparasites. Host and parasite trees were compared in order to assess possible congruence between phylogenies of interacting taxa.

-Bloodparasites in German birds of prey and owls

More than 1000 blood smears are actually under investigation to study which endoparasite species such as the haemosporidia (Plasmodium, Haemoproteus, Leukozytozoon), Trypanosoma and Mikrofilaria do occure in German birds of prey and owls. The pygmy owl ( Glaucidium passerinum ) was found as new host for the flagellat Trypanosoma avium (KRONE, 1996).

Blood parasites

-Prevalence of Trichomonas gallinae in northern goshawks ( Accipiter gentilis ) from a urban and rural habitat

During the breeding season 1997 cases of clinical diseased northern goshawks were reported in Berlin. In the breeding season 1998 and 1999 northern goshawks from Berlin and Brandenburg were scanned for Trichomonas gallinae. The comparison of the habitats will reveal differences between northern goshawks from Berlin (feeding mainly of feral pigeons) and Brandenburg (very few feral pigeons in the diet).

                                                          
                                       Goshawk                                                          Trichomonas gallinae

  -Health status of the Eurasian Cranes (Grus grus) in Germany

The analysis of natural and anthropogenic causes of disease and death of the Eurasian Cranes in Germany is the main aim of this project. Beside studies on the crane health status, new aspects of diseases, being a potential endangerment to this species, are investigated more closely. The identification of  important foci of infection at roosts, resting places and feeding grounds, in combination with findings of the disease research, should provide advisory information to the crane conservation in Germany.

                        
                   February 2006: In typical V-formation cranes coming back                              A pair of cranes in the North of Brandenburg
                from their Wintering places in Southern Europe and North Africa

2. Parasitic fauna in Carnivores

-Helminths of Carnivores

Heteroxenous parasitic worms which life-cycles are involved in predator-prey systems are under investigation.

 -Endoparasites in wild cats (Felis silvestris) from the Eifel region

In a project on wild and domestic cats from the Eifel region, Germany the spectrum of endoparsites between the two cat species can be compared. So the idea of wild cats to be a reservoir for endoparasites of domestic cats can be answered.

Service

Parasitological examination of samples from the field station and other persons.