Strongyloides stercoralis is the most common human parasitic nematode capable of completing a life cycle and proliferating within its host. The majority of patients with strongyloidiasis have asymptomatic infection or mild disease. However, when autoinfection occurs, a high number of infecting larvae can gain access to the bloodstream by penetrating the intestinal mucosa leading to severe hyperinfection and the development of disseminated strongyloidiasis.(1) A close relationship between  human T cell lymphotropic virus type I (HTLV-1) and Strongyloides stercoralis has been reported from endemic regions like Japan and Jamaica.(2)This has not been reported from  India where the prevalence of HTLV-I is very  low especially in HIV seronegative persons.(3)

Case report

A 45-year old Keralite man, living in Sikkim presented with a one-year history of recurrent vomiting, borborygmi, abdominal distention relieved by  vomiting, intermittent watery loose stools and weight loss. Nine months before, he had been treated for tuberculous lymphadenitis and had completed the full course. On examination, he was emaciated and had mild pallor and pedal oedema.

Laboratory examination revealed a haemoglobin of 10.2 g/dl with a mean corpuscular volume of 90.9 fL. Total serum proteins were 5.8 g/dl (normal 5-7g/dl) and serum  albumin was 2.5 g/dl (normal 3.5-5 g/dl). Stool microscopy on three consecutive days showed numerous Strongyloides larvae. Barium meal follow through study revealed effacement of mucosal folds in the 3rd and 4th parts of the duodenum and multiple small sacculations arising from the superior portion of the 3^rd part of duodenum and jejunum with normal ileum and ileocaecal junction. Endoscopic biopsies depicted Strongyloides infestation in the stomach, duodenum and jejunum. Colonoscopy was normal and colonic and ileal biopsies were unremarkable. He was treated with albendazole for 5 days. His stools continued to show Strongyloides larvae and he was hence given a course of ivermectin 200 µg/kg in 2 doses at 2 week intervals. His symptoms improved significantly but his stool persistently revealed Strongyloides larvae.

Since he had had extrapulmonary lymph node tuberculosis recently and persistent Strongyloides infestation resistant to standard therapy, underlying immunosuppression was considered and investigated into. HIV serology was negative. The association between persistent and severe strongyloidiasis was kept in mind, and HTLV-I serology was done and found positive. His wife tested negative. He was given 3 courses of ivermectin. Within a few weeks, his serum albumin improved to 4 g/dl. The patient remains well. He is being kept under close surveillance for other consequences of HTLV-I infection like lymphoma and paraparesis. During his third annual visit Strongyloides larvae were positive on stool microscopy. He was again treated with 2 courses of ivermectin at 3 month intervals.

Discussion

Human T-cell lymphotropic virus type I has been associated with a malignant disease namely, adult T-cell leukaemia/lymphoma and several non-malignant conditions, notably the chronic neurodegenerative disorder, HTLV-I associated myelopathy (also known as tropical spastic paraparesis), infective dermatitis of children and uveitis. HTLV-I has a worldwide distribution with major endemic foci in the Caribbean and southern Japan. The public health importance is confirmed by the major routes of transmission, which are mother-to-child, blood transfusion, and sexual contact. Unfortunately, no vaccine is available yet and there is no proven treatment for advanced HTLV-I disease.(4)

In a prospective study of patients with intestinal strongyloidiasis without known immunosuppression who failed to respond to standard therapy with ivermectin or  thiabendazole (failure was defined as one positive stool examination at the post-therapy follow up), 75% were positive for HTLV-I infection.(5) The association of HTLV-I and  strongyloidiasis has been shown to be fatal.(6)

Strongyloides stercoralis patients with HTLV-1 co-infection have modified immunological responses against parasite antigens and co-infection has clinical implications for treatment of strongyloidiasis. The high production of IFN-gamma observed in patients who are co-infected decreases  the production of IL-4, IL-5, IL -13 and IgE molecules that participate in the host defence mechanism against helminths. Moreover, strongyloidiasis is harder to treat in patients co-infected with HTLV-1. Alterations in the immune response against Strongyloides stercoralis and decrease in the efficacy of anti-parasitic drugs are responsible for the increased prevalence of Strongyloides stercoralis among HTLV-1 infected subjects and make HTLV-1 infection the most important risk factor for disseminated strongyloidiasis.(1)

Hence it is important to investigate for coexistent HTLV-I infection in patients with treatment resistant and severe strongyloidiasis as frequent recrudescences are common in these patients. Treatment of HTLV-I is not indicated for asymptomatic individuals, and management is confined to the early diagnosis of clinical manifestations and the prevention of transmission to others. The latter includes avoidance of breast feeding in endemic areas, screening of blood donors, as well as promotion of safe sex and discouraging needle sharing.

References

1.     Carvalho EM, Da Fonseca Porto A. Epidemiological and clinical interaction between HTLV-1 and Strongyloides stercoralis. Parasite Immunol. 2004;26:487–97

2.     Hirata T, Uchima N, Kishimoto K, Zaha O, Kinjo N, Hokama A, et al. Impairment of host immune response against Strongyloides stercoralis by human T cell lymphotropic virus type 1 infection. Am J Trop Med Hyg. 2006;74:246–9.

3.     Kumar H, Gupta PK. Is seroprevalence of HTLVI/III among blood donors in India relevant? Indian J Pathol Microbiol. 2006;49:532–4.

4.     Manns A,  Hisada M,  La Grenade L. Human T lymphotropic virus type I infection. Lancet. 1999;353:1951–8.

5.     Terashima, Alvarez H, Tello R, Infante R, Freedman DO, Gotuzzo E. Treatment failure in intestinal strongyloidiasis- an indicator of HTLV-I infection. Int J Infect Dis. 2002;6:28-30.

6.      Adedayo AO, Grell GA, Bellot P. Case study: Fatal strongyloidiasis associated with HTLV-I infection. Am J Trop Med Hyg. 2001;65:650–1.