What is the relationship between Heterakis gallinarum and Histomonas meleagridis: A question for parasitologist
Histomonas meleagridis is said to be one of the major pathogenic parasites of Turkey (it causes blackhead disease or Histomoniasis) while Heterakis gallinarum can be mildly pathogenic in domestic fowl (particularly in chicken and turkey).
There are different types of association between different species some of which can be mutual, parasitic or commensal. Experiments by experts in parasitology have shown that the longevity of Histomonas meleagridis is extended because of its association with Heterakis egg. That is Histomonas cannot survive for a long time on its own in the environment but it can survive up to two years when it is in Heterakis egg.
It can be said that the Heterakis egg, which is a typical ascarid egg and as such has a thick shell can help protect the Histomonas especially to avoid it being desiccated. However, I wonder when the association started and what factors influences the association apart from the fact that both species, that is Histomonas and Heterakis, share same predilection site in the Chicken where the Histomonas is said to be non-pathogenic and as such the Histomonas can easily be incorporated into the Heterakis egg during the egg formation. Then the question will be, is the egg shell formed inside the Heterakis genital system or outside (in the host)?
If it is inside, then it is likely that the Histomonas infests or lives inside the Heterakis and as such can easily be incorporated inside the egg during the egg formation before the egg shell is formed. The possibility of such infestation cannot be ruled out because even bacteria are infected or parasitized by viruses (bacteriophages). Therefore it is possible that Histomonas, a protozoa can infest Heterakis, a nematode and such association maybe pathogenic or not or the Histomonas may only use the association to get to the final host, Turkey.
Lastly, Heterakis gallinarum and those animals that act as reservoir of Heterakis egg are important in the epidemiology of Histomonas meleagridis but how the associated started and the type of association should also be of importance. That is why I wonder if parasitologists know the type of association or relationship that exists between Heterakis and Histomonas.
That is my question for parasitologist.