Molecular tool for identification of parasitic worms of birds from natural ecosystems - development and validation
Project duration: 2023 - 2026
Keywords: Bulgaria, Helminth parasites, Trematoda, Cestoda, Acanthocephala, Nematoda, birds, diagnostics, barcoding, metabarcoding

Parasitic worms or helminths parasitize all groups of vertebrates and humans and some of them cause disease. Little is known about the parasites of wild animals. According to some studies, their species diversity is 2.2 to 7.8 times that of the hosts, and only 5-15 % of vertebrate helminths have been described. Despite the hidden lifestyle that parasitic worms have, they influence the intraspecific and interspecific interactions of their hosts, their population dynamics and their evolution by affecting behavior, individual growth, fecundity and mortality. Parasites also play an important role in ecosystem functioning. Many of the helminths are highly specialized to their host, which is the result of their long co-evolutionary history; therefore, the extinction of the host leads to the extinction of its parasites and a corresponding cascading loss of biodiversity.

Endoparasitic worms are a phylogenetically heterogeneous group of organisms adapted to live in different organs and systems of their hosts. Many helminths have complex life cycles involving one to two obligatory intermediate hosts (invertebrates in most cases) and often use paratenic hosts to reach the final host. The majority of helminths leave the final host only in the form of eggs or larvae, and the microfilariae of filarial nematodes circulate in the blood or peripheral lymphatic vessels of the derma and use blood-sucking insects and ticks as vectors in which they undergo development and use them to reach the new definitive host.

Accurate identification of parasites is of paramount importance in answering fundamental questions about their species diversity and the processes determining it. What are the pathways for the formation of parasite-host relationships in the course of evolution? What are the impacts that parasites have on hosts at the species and population level, as well as at the level of the entire ecosystem? From a practical point of view, the timely identification of helminthiases in zoos, as well as in breeding centres for rare animals, can be decisive for the health of valuable animals, and also can help to recognize the agent of the parasitic disease and to manage its elimination. Parasites can also affect the success of conservation activities such as translocations, introductions and reintroductions of rare animals into the wild.

Rapid and accurate morphological identification of helminth parasites in wildlife is severely limited due to the specificities of the group. Adult helminths are located in the organs and systems of their hosts, and the traditional approach of collecting them for taxonomic purposes may happen only after natural death or euthanasia of the host. The eggs and larvae of the parasitic worms released into the environment with feces do not have enough characters in order to allow morphological identification at the species level. Identification of helminths is time-consuming and severely hampered by greatly reduced taxonomic expertise worldwide.

Birds are hosts of taxonomically, systematically and ecologically diverse helminths. Despite the small territory of Bulgaria, more than 400 avian species have been recorded for the country's fauna since 1950. Prerequisites for the large number of birds are the diverse habitats as well as the geographical position of the country, used as nesting or wintering grounds. Some of the largest bird migration routes in Europe pass through Bulgaria. Birds are an important component of ecosystems and are used as an indicator of their condition. Most species of wild birds, their eggs and habitats in the European Union are protected by DIRECTIVE 2009/147/EC of the European Parliament and of the Council. Despite the importance of birds for the health of ecosystems, there is currently no developed methodology for performing non-lethal helminthological studies on them and this makes it impossible to carry out routine monitoring of their helminthic diseases.

The aim of the present project is to develop and provide the scientific community with a tool for rapid and accurate identification of parasitic worms in birds based on molecular barcoding and metabarcoding, as well as for the diagnosis of helminthoses (helminth diseases) of birds. The collection of deposited sequences obtained in the course of the project will provide a means for rapid and accurate determination of adult helminths and their eggs and larvae by non-specialist taxonomists for a large proportion of species in Europe. The method will be available to be used by forestry, zoos and conservation programs concerned with the breeding of rare animals and their return to the wild environment, disease control services and a variety of studies on the dynamics of parasitic diseases. In addition to these applied studies, the method will also contribute from a biogeographical point of view to reveal the ranges of parasite species and also to obtain comprehensive data on the host range, studying parasite life cycles and the transmission pathways of parasitic helminths.

  • Institute of Biodiversity and Ecosystem Research – Bulgarian Academy of Sciences

Contact person: Yasen Mutafchiev,