Prevalence and Histopathological Studies on Intestinal Cestode Parasite of Avian Host Gallus Domesticus (L) From Nashik Region, Maharashtra State, India

The lowest infection is recorded in rainy season and highest in summer season, may be due to life cycle stages and intermediate host availability increases in winter and became adult in definitive host in summer. No nematode and trematode parasite were considered and identified during the study period. Cysts were found deep in submucosa, although touches to serosa. The non-penetrative type of worms is Cotugnia sp. and Thaparea sp.; while the penetrative type of worm is Raillietina sp. and Paruterina sp. Free gravid segments mostly found in the posterior region of intestine while mature segments are freely suspended from scoleces in the lumen of intestine, only scoleces are attached, either superficially (non-penetrative type) or deep in submucosa (Penetrative type). Keywords: Cestode, histopathology, prevalence, hold-fast organs, Penetrative scolex

​The Histopathology of Alimentary Canal of Stinging Catfish Heteropneustes fossilis (Bloch, 1794), Susceptible for Trematodes Incursion

Background: Heteropneustes fossilis (Bloch, 1794) is one of the popular freshwater fish known for its food quality and nutritional value. This study was undertaken with an aim to find out histopathological changes in the intestine of freshwater fish Heteropneustes fossilis, host of trematode parasite Masenia vittatusia Agarwal, 1963. Methods: The intestine of uninfected fish used to determine normal anatomy, while infected intestine to determine pathological changes. The normal histological procedure was followed, which included fixing, rinsing, dehydrating and embedding of tissue. Tissue was cut in 4-6 µm thick sections using a rotary microtome. Haematoxylin and eosin stains were used. Result: The highest damage was observed in the mucosal layer with ruptured and fused microvilli, hyperplasia of villi, damaged columnar epithelium layer and spread of loose connective tissue into the lumen. Other degenerative modifications included hypertrophy of blood vessels in mucosa and muscularis part, some of them ruptured might be the cause of haemorrhage inside the layers. Other changes include variation in the routine shape of all three layers. The mucosal layer showed aggregation of lymphocytes and mast cells as well.

Trematode parasite cercariae as food in model freshwater trophic interactions

Free-living parasite stages are important but often overlooked components of ecosystems, especially their role(s) in food webs. Trematode parasites have complex life cycles that include a motile transmission phase, cercariae, that are produced in great quantities within aquatic snail hosts and join the zooplankton community after emerging. Here I examined how cercariae presence affected the population abundance of a common freshwater zooplanktonic animal (Daphnia) when predators were present. I also sought to determine the pathways taken by cercariae-derived carbon within a model freshwater food web by using the stable isotope 13C as a tracer. I found that Daphnia population abundance positively benefitted from cercariae presence when larval dragonfly predators were present, serving as alternate prey. I also found that 13C was an effective tool to track the flow of cercarial carbon, demonstrating high consumption by benthic consumers, as well as the utility of this method for use in future studies.

Effects of a Cyanobacterial Toxin and Macrophyte composition on Amphibian Parasitism

Amphibians are experiencing global declines with habitat loss and degradation, and infectious diseases as major contributors. Environmental changes such as eutrophication and climate alterations can cause the proliferation of primary producers, including cyanobacteria, and both native and invasive macrophytes. Cyanobacterial blooms can be toxic due to the production of microcystins such as MC-LR, and invasive macrophytes can alter the structural complexity of aquatic habitats – both can affect host-parasite dynamics. I examined the effects of MC-LR on larval amphibian susceptibility to infection by a trematode parasite as well as host growth and anti-parasite behaviour, finding increased susceptibility to infection at low concentrations. I also investigated how MC-LR affected the longevity and activity of trematode infectious stages (cercariae), and demonstrated variable effects among species. Lastly, I examined how environmental structural complexity, modeled as macrophyte complexity and density, affected tadpole infection by a trematode parasite and host anti-parasite behaviour but found no impact.

Trematode parasite cercariae as food in model freshwater trophic interactions

Free-living parasite stages are important but often overlooked components of ecosystems, especially their role(s) in food webs. Trematode parasites have complex life cycles that include a motile transmission phase, cercariae, that are produced in great quantities within aquatic snail hosts and join the zooplankton community after emerging. Here I examined how cercariae presence affected the population abundance of a common freshwater zooplanktonic animal (Daphnia) when predators were present. I also sought to determine the pathways taken by cercariae-derived carbon within a model freshwater food web by using the stable isotope 13C as a tracer. I found that Daphnia population abundance positively benefitted from cercariae presence when larval dragonfly predators were present, serving as alternate prey. I also found that 13C was an effective tool to track the flow of cercarial carbon, demonstrating high consumption by benthic consumers, as well as the utility of this method for use in future studies.

Effects of a Cyanobacterial Toxin and Macrophyte composition on Amphibian Parasitism

Amphibians are experiencing global declines with habitat loss and degradation, and infectious diseases as major contributors. Environmental changes such as eutrophication and climate alterations can cause the proliferation of primary producers, including cyanobacteria, and both native and invasive macrophytes. Cyanobacterial blooms can be toxic due to the production of microcystins such as MC-LR, and invasive macrophytes can alter the structural complexity of aquatic habitats – both can affect host-parasite dynamics. I examined the effects of MC-LR on larval amphibian susceptibility to infection by a trematode parasite as well as host growth and anti-parasite behaviour, finding increased susceptibility to infection at low concentrations. I also investigated how MC-LR affected the longevity and activity of trematode infectious stages (cercariae), and demonstrated variable effects among species. Lastly, I examined how environmental structural complexity, modeled as macrophyte complexity and density, affected tadpole infection by a trematode parasite and host anti-parasite behaviour but found no impact.