The parasitic infestation has worldwide prevalence and it affects almost all age groups and both the sex. The developing countries are more prone to intestinal and extra-intestinal parasitic infestations. The morbidity and mortality due to parasitic infections are higher due to an increase in the prevalence of immunocompromised conditions, nutritional deficiencies, chronic diarrhoea, and impaired development in children. Parasite lives in (endoparasite) or on (ectoparasite) another organism called its host. The host suffers various diseases, infections and discomfort as the organism obtain nourishment and protection [1,2]. The tissue damage caused by the parasite can be either due to physical pressure or toxic secretory products which may lead to hypersensitivity reactions. Tissue response produced by these parasites on histopathology provides a clue in the search of parasites and confirm the diagnosis. Eosinophilic infiltration, abscess formation and granulomatous reaction are the most common tissue responses encountered due to parasites. In the case of dead or calcified parasites there is no tissue response identified [3,4]. The relevant clinical information and histomorphological features in the tissue section would help to identify a particular organism.

Setting: Department of pathology, Vinayaka Missions Kirupananda Variyar Medical College & Hospital, a tertiary care centre in Salem, Tamil Nadu.

Duration and type of study: A Retrospective descriptive study conducted for a period of 3 years from January 2018 to December 2020.

Sampling methods: All parasitic infestations reported on histomorphology in the department of pathology.

Sample size: 11 cases

Inclusion criteria: All parasitic infestation diagnosed in histopathology on tissue sections.

Exclusion criteria: Parasitic infestations diagnosed in fine needle aspiration cytology. Parasitic infestation diagnosed in brush and exfoliative cytology smears. Parasitic infestations diagnosed in smears from fluid cytology and peripheral blood smears.

Figure 1: Age distribution

Table 2: Comparison of incidence of parasitic infestation in various studies [5,6,7,8,9].

Parasitic infestation is a public health problem in endemic countries with a temperate climates. Very few studies have been conducted on the presence of different parasites in the tissue section as biopsies are usually not necessary in most cases. This is done for diagnostic purposes, to identify other entities and in complicated cases resection is done. Many studies have been conducted on stool samples, as stool microscopy being the faster and preferred method but is not relevant in all types of parasites, serological tests can be used for supporting diagnosis [4,10]. Early diagnosis of a parasitic infestation can help for the immediate onset of treatment. Hydatid cyst or Echinococcosis caused by dog tapeworm is a zoonotic helminth that affects mainly the liver and lungs in humans. The feco-oral route is the common mode of spread where after ingestion of eggs by a human they penetrate the intestinal mucosa they enter the portal circulation and carried to the liver, lung and other organs to develop into fluid-filled cyst [11].

Figure 3: Intramuscular cysticercosis [H -E stain, x10]

The luminal obstruction can cause an increase in intraluminal pressure which impairs appendix wall blood circulation with mucosal damage, inflammation, sepsis, necrosis and perforation [14]. All 5 cases in our study were clinically diagnosed as appendicitis where the intraluminal parasite was an incidental finding, 3 cases showed eosinophilic with acute inflammatory infiltrate, 2 cases showed only acute inflammatory infiltrate (Fig.4). It is very important to receive antihelminthic treatment even after appendicectomy as the root cause of the disease is not treated [13]. In cases of appendicitis, appendicectomy and unnecessary surgery can be avoided if pre-operative diagnosis of the luminal parasite can be made because clinical management of these infections is different from that for classical appendicitis [13,15].

Figure 5: Hard tick (a) whole section of tick with capitulum (arrow), cuticle structures (arrow head) [H -E stain, x10]. (b) cuticle (arrow), midgut epithelium (arrow head), salivary gland (SG), Musculature (M) [H -E stain, x40].

Parasitic lesions can show different clinical manifestations. Among the 11 cases throughout 3years, only 3 cases of hydatid cyst and one case of cysticercosis were clinically diagnosed. Rest other 7 cases were incidental findings on histopathological examination. With the increase in the immunocompromised state, overuse of antibiotics, malnutrition, change in life habits is a major concern, calling for the cautious eye to look for parasitemia in tissue sections. As there is no vaccine for such infections, early diagnosis and systemic medications will decrease the morbidity and mortality, hospital and monitory burden on the patients too. This study emphasizes the need for careful history taking and histopathological examination of these lesions which helps in diagnosis. It also helps us to understand the interactions between parasites and host tissue and aids in specific treatment for the patient.

Detection of various tissue responses and presence of parasite seen on histopathological examination confirms the primary cause of disease that helps to provide specific treatment for the patients.

Dr. Poovizhi Inbasekaran: data collection, data compiling, literature review, manuscript preparation, manuscript editing. Dr. Thamilselvi R: manuscript editing, final approval. Dr. Megala C: data collection, manuscript editing Dr. Anbu Lenin K: manuscript editing