Avitellina centripunctata is a tapeworm parasite that has mainly sheep, goats and occasionally cattle, dromedaries and other wild and domestic ruminants as final hosts.
It is quite common in arid regions of Africa, Asia and Europe. Avitellina woodlandi is a related species found in dromedaries in Africa.
The infections with Avitellina are called avitelliniasis or avitellinosis.
Avitellina centripunctata tapeworms do not affect dogs, cats, horses, swine, or poultry.
Are animals infected with Avitellina centripunctata contagious for humans?
NO. The reason is that Avitellina centripunctata is not a human parasite. See the life cycle below.
Final location of Avitellina centripunctata
The predilection site of adult Avitellina tapeworms in their final hosts (sheep, goats, cattle, etc.) is the small intestine.
Anatomy of Avitellina centripunctata
Adult Avitellina tapeworms are up to 3 m long and about 3 mm wide. The segments are very short and segmentation of the strobila is hardly noticeable.
The main body (or strobila) has up to thousands of segments (called proglottids). The segments are very short and segmentation of the strobila is hardly noticeable. The segments is much broader than long. As in all tapeworms, each segment has its own reproductive organs of both sexes (i.e. they are hermaphroditic) and excretory cells known as flame cells (protonephridia).
The reproductive organs in each segment have a common opening called the genital pore. In young segments all these organs are still rudimentary. They develop progressively, which increases the size of the segment as it is pushed towards the tail. Mature gravid segments are full of eggs (several thousands) and detach from the strobila (i.e. the chain of segments) to be shed outside the host with its feces.
Otherwise, as other tapeworms, they have neither a digestive tube, nor a circulatory or respiratory systems. They don't need them because each segment absorbs what it needs directly through its tegument. Individual gravid segments in the feces are visible by the naked eye.
The eggs have an oval shape, are rather small (~20x45 micrometers) and embryonated.
Life cycle and biology of Avitellina centripunctata
The life cycle of Avitellina centripunctata is not completely elucidated. It has an indirect life cycle with ruminants (mainly sheep and goats) as final hosts, but the intermediate hosts are still unclear. It seems that certain oribatid mites (also called "moss mites" and "beetle mites") and barklice (Psocoptera) are involved.
The adult worms produce eggs that are shed with the feces of the host, either already free or included in gravid segments. Depending on the species and the region they can survive for months in the environment and some may survive cold winters, but they are very sensitive to dessication. The intermediate hosts ingest the eggs, which develop to infective cysticercoids in their body cavity.
The final host becomes infected after ingesting such contaminated intermediate hosts while grazing. After digestion the released cysticercoids attach to the gut's wall and develop to adult tapeworms within a several weeks, depending on the worm species and the final host.
Harm caused by Avitellina centripunctata, symptoms and diagnosis
Most infections with Avitellina centripunctata are benign and produce no clinical signs. Even massive infections can remain asymptomatic. Nevertheless, they compete for nutrients with the host and their presence can negatively affect productivity. There are some reports that the general livestock condition improved after treatment.
Diagnosis is based on fecal examination for the presence of gravid segments (proglottids, may look lice rice grains) or of eggs with a characteristic morphology. After necropsy the large tapeworms are easily seen inside the gut.
Prevention and control of Avitellina centripunctata
It is not possible to eliminate the mites or other intermediate hosts in the pastures. The use of insecticides for this purpose is not advisable, because it is more expensive than the potential economic loss due to the infections, and because it detrimental effect on the environment: it would kill not only the intermediate hosts, but numerous beneficial insects as well.
Susceptible livestock, particularly lambs can be treated with anthelmintics effective against tapeworms. They contain either broad-spectrum active ingredients (e.g. albendazole, fenbendazole, mebendazole, oxfendazole, etc.) or specific taenicides (e.g., niclosamide, praziquantel, etc.). Specific taenicides are also used in mixtures with nematicides (e.g. ivermectin, levamisole, etc.).
Excepting slow-release boluses, most wormers kill the worms shortly after treatment and are metabolized and/or excreted within a few hours or days. This means that they have a short residual effect, or no residual effect at all. As a consequence treated animals are cured from worms but do not remain protected against new infections. To ensure that they remain worm-free the animals have to be dewormed periodically, depending on the local epidemiological, ecological and climatic conditions.
Other classic livestock anthelmintics such as macrocyclic lactones (e.g. ivermectin, doramectin, moxidectin, etc.), levamisole, tetrahydropyrimidines (e.g. pyrantel, morantel) and piperazine derivatives are not effective at all against Avitellina or whatever tapeworm.
There are so far no vaccines against Avitellina centripunctata. To learn more about vaccines against parasites of livestock and pets click here.
Biological control of Avitellina centripunctata (i.e. using its natural enemies) is so far not feasible.
You may be interested in an article in this site on medicinal plants against external and internal parasites.
Resistance of Avitellina centripunctata tapeworms to anthelmintics
So far there are no reports on resistance of Avitellina centripunctata tapeworms to anthelmintics.
This means that if an anthelmintic fails to achieve the expected efficacy, chance is very high that it is not due to resistance. Either the product was used incorrectly or it was unsuited for the control of these parasites. Incorrect use is the most frequent reason for failure of antiparasitic drugs.
Ask your veterinary doctor! If available, follow more specific national or regional recommendations for Avitellina control.