With the emergence of AIDS, parasitic diarrhea has gained significance, as it is one of the important causes of morbidity and mortality. The line of treatment being different for diverse parasites necessitates a definitive diagnosis and study of the etiological agents causing diarrhea, especially when it can be fatal in this vulnerable group of individuals.
Our study showed prevalence of more males than females (p < 0.05). Predominance of male cases may be due to their migration to the metropolitan cities in search of work. Staying away from the families for longer periods and males being promiscuous by habit resulted in them, acquiring HIV infection.
The drugs of choice for diarrhoea for practising clinician were ornidazole, metrogyl, nitazoxamide and albendazole. However, Sengupta et al observed that paramomycin was effective against cryptosporidiosis . However, HAART added to the efficacy of the aforementioned anti protozoals and 36.6% patients were found to have a rebound in their CD4 cell counts. A study conducted by Guadalupe et al, showed that viral suppression is more effective in GALT (gut-associated lymphoid tissue) of patients with primary HIV infection than patients having chronic HIV infection during HAART . They found delay in restoration of gut mucosal immune system of patients with chronic infection as gut acts as a viral reservoir and keeps from eradicating the virus.
In this study we came across patients ranging from initial to advanced stages of the disease. There were 69.3% patients with chronic and 30.6% patients with acute diarrhea (p < 0.05). Recurrent episodes and presence of diarrhea even at higher CD4 levels can be attributed to reduced intestinal mucosal immunity .
The percentage of parasite isolation in our study was 78.5% in acute and 50.7% in chronic cases. A similar study conducted in the same set up by Attili et al showed lower isolation rates . This discordance in the results could be due to more than one technique used in this study for identification, which might have increased the sensitivity. Lower isolation rate of parasites in chronic cases was because most of the patients with chronic diarrhoea were on empirical antidiarrheal treatment. Moreover, in this country anti-diarrhoeal drugs are freely available across the counter in the drug store even without prescription.
In this study it was observed that probability of finding a pathogen from watery and semi formed stools was four times greater as compared to formed stools . This can be attributed to greater shedding, more inflammatory response and greater virulence of the pathogens causing watery diarrhea.
Samples collected from the controls coming from the same environmental background helped in tracing the source of infection. Parasite like Cryptosporidium spp. isolated from both the groups indicated water as the main source of infection, which highlighted poor sewage disposal practices and sewage spills. Presence of Hookworm indicated lack of sanitation and low socio-economic status of the cases coming from rural areas.
Cryptosporidium spp. (39.8%) was the most commonly isolated protozoan followed by Microsporidia spp. (26.7%). As compared to the controls, the observed incidence of these organisms in HIV patients was significantly higher (p < 0.05). Another study conducted by Samantaray et al, also showed similar isolation rates in HIV patients  whereas, in a study of Southern India lesser number of Cryptosporidium spp. (9%) were isolated . A study conducted in Mumbai showed the infection rate of Microsporidia spp. in HIV patients as 17.18% . On the contrary our study detected 26.7% of Microsporidia spp. This increase in isolation rates could be due to the fact that the numbers of cases studied were much higher in our study as compared to the study of Siddhartha et al . When compared to other studies of Southern India, isolation rate of Isospora belli (0.5%) was lower in our study . This discrepancy in the findings maybe attributed to geographical variation. Calcoflour White staining technique, which is a screening method, identified the Microsporidia spp. However, its presence will be confirmed later by Chromotrope 2R staining method in order to avoid any false positive results, if any. The clinical picture and the microscopic examination of the dysenteric stools revealed haematophagous trophozoites suggesting that the Entamoeba spp. isolated were presumably that of Entamoeba histolytica. This screening method was adopted due to lack of facilities for isoenzyme analysis and other tests to differentiate it from Entamoeba dispar . Although the study was conducted to screen for the enteric protozoan, we came across 7.65% cases where helminths like Hookworm, H. nana and Trichuris trichiura co-existed with protozoa. These were probably flushed from the intestine because of diarrhoea or expelled after treatment. Therefore, we reported their presence as and when we came across the helminths during stool examination.
It was found that 6.8% patients had acquired the HIV through homosexual route. Giardia spp. (64%) was present more in this group of people as compared to those who had heterosexual practice. Our findings are in accordance with Curry et al .
The maximum parasitic isolation was in the group of patients who had CD4 cell counts below 200 cells/μl and Cryptosporidium spp. was found to be the most commonly acquired protozoa causing chronic diarrhoea. The isolation rates decreased with the increase in the CD4 cell counts. This finding is in accordance with the study conducted by Attili et al. They also found an inverse correlation between CD4 counts and isolation rates of parasites from diarrhoea patients .
Key climatic variables, particularly humidity and temperatures have always had a relationship to waterborne diseases. The Milwaukee episode of 1993, which affected 403,000 people, is a commonly quoted waterborne Cryptosporidiosis outbreak . The advent of rainy season marks the beginning of many infectious diseases. In our work too, the maximum parasitic isolation was during rainfall, with Cryptosporidium spp. at the top of the list followed by Giardia spp. (p < 0.05). We observed that isolation rate of Cyclospora spp. peaked during the summer and was significantly higher as compared to in the other seasons (p < 0.05). This is because sporulation or maturation of the immature oocysts excreted in the faeces depends on warm temperatures .
Limitations of the study
Immune restoration as detected by CD4 counts was clinically assessed.
Calcoflour White staining for Microsporidia spp. is merely a screening method. However, the authors have plans to carry out identification techniques like Chromotrope 2R staining to confirm the results.
The study was done as and when the symptoms of diarrhoea appeared and accordingly they were categorised season wise. It is difficult to establish the time period of initiation of infection.