A prospective study of seroprevalence of Toxoplasmosis in general population, and in HIV/AIDS patients in Bombay, India.YV Meisheri, S Mehta, U Patel
Department of Medicine, Seth G.S. Medical College, Parel, Bombay, India. , India
Two hundred and seventy nine sera (age group 13-50 years) were tested for antitoxoplasma IgG/IgM antibodies by ELISA techniques; the diagnostic titer for positive test is 10 iu/ml or > 1:100. Sera were obtained from (i) 165 (100 men/65 women) healthy adult voluntary blood donors (HIV, HBsAg, VDRL negative); (ii) 89 consecutive HIV/AIDS patients (82 men/7 women); and (iii) 25 patients (HIV negative: 12 men/13 women) treated for cerebral Tuberculoma or Neurocysticercosis during this study from January 1996-June 1997. The overall seroprevalence was 30.9% (51/165) in the immunocompetent adult (group i) 34% (34/100) men and 26.2% (17/65) in women [range: 10-899 iu/ml; (mean: 376.8)]. In HIV infected hosts the seroprevalence [range: 21-340 iu/ml; (mean; 180)] was 67.8% (56/82 men, 04/07 women). The seroprevalence was 20.5% (8/39), 32.8% (22/67), 34.8% (16/46) and 38.4% (5/13) in the 2nd, 3rd, 4th and 5th decades respectively in healthy adults. In HIV/AIDS patients, 69% (29/42) in the 3rd and 70.6% (24/34) in 4th decade were seropositive. The risk of cerebral Toxoplasmosis (encephalitis-02, granuloma-24) was 43.3% (26/60, mean 250 iu/ml). The seroprevalence was 28% in group iii (range 12-80 iu/ml, mean 21 iu/ml). Anti-toxo IgM was negative in all. Primary Toxoplasma infection appears to be subclinical and prevalent throughout life. T. gondii has emerged as an important opportunistic infection in HIV/AIDS patients in Bombay. Recrudescence of cerebral toxoplasmosis (CTOX) is observed with low IgG response during mid-late stage of the disease, as seen in our patients (mean IgG 250 iu/ml, CD4+ = 283/cmm (range 43-504 in 5 patients). Primary prophylaxis for CTOX seems rationale and can be targeted to asymptomatic HIV/AIDS population at risk who are seropositive for T. gondii (mean IgG 111.5 iu/ml in our study). The very high predictive value of a negative test for TOX remains the best serological parameter for excluding acute episode of TOX.
Keywords: AIDS-Related Opportunistic Infections, epidemiology,Adolescent, Adult, Animal, Antibodies, Protozoan, blood,CD4 Lymphocyte Count, Enzyme-Linked Immunosorbent Assay, Female, Human, Immunoglobulin G, blood,Immunoglobulin M, blood,India, epidemiology,Male, Middle Age, Prospective Studies, Seroepidemiologic Studies, Support, Non-U.S. Gov′t, Toxoplasma, immunology,Toxoplasmosis, epidemiology,Toxoplasmosis, Cerebral, epidemiology,
Toxoplasmosis has been reported as the commonest opportunistic infection in HIV/AIDS patients in developed countries,. Serological testing has become the routine method of diagnosis of Toxoplasmosis. The Sabin-Feldman dye test, the indirect fluorescent antibody test and the ELISA, all satisfactorily measure circulating IgG antibody. Positive IgG titers >1:10 or 1 i.u. can be detected as early as 2-3 weeks after infection; reach maximum titer of 300 to 3000 iu. within 2 months, and decline to a new baseline level that persists for life. It is necessary to measure the IgM titer in concert with the IgG titer to establish the time of infection. IgM antibodies appear within a few days and reach a maximum titer within 4 weeks. This test can turn negative within 4-12 weeks. But, IgM can be detected at very low titer, for months/even years in a minority of patients, particularly with ELISA tests. In patients with AIDS, presence of IgG and neuroradiologic findings consistent with Toxoplasmosis are grounds for a presumptive diagnosis. Serologic evidence of infection virtually always precedes the development of Toxoplasma encephalitis.
With galloping epidemic of HIV infection in India, we had also witnessed AIDS patients with cerebral Toxoplasmosis during 1994-1995. These were admitted under our care with acute neurological syndrome(focal/non-focal),had high IgG but negative IgM antitoxoplasma antibody, single/multiple ring enhancing lesions on CT/MRI of brain(location: basal ganglia, thalamus, corticomedullary junction). They showed 75% clinical response within 5-7 days and 75-100% clearance of the CT/MRI lesions within first 3 weeks of anti-toxoplasma treatment.
Prompted by these observations and encouraged by the favorable treatment outcome, we undertook this prospective study. Our aim was to establish seroprevalence of acquired primary toxoplasma infection in the general population and occurrence of latent infection with recrudescence in HIV/AIDS patients for obvious therapeutic implications.
Study period : January 1996-June 1997; Age-group:13-50 yr.
Place : The King Edward Memorial Hospital, Mumbai.
Study Population : (Both genders) This was categorised as:
Group A. General population: 165 healthy voluntary blood donors (100 men/65 women, age group-18 to 50 yr.) from our blood bank formed this group. Each serum sample was tested for HIV, VDRL, HBsAg as a protocol of the blood bank & was negative. These samples were processed for anti-Toxoplasma IgG, IgM by ELISA techniques (Sensitivity-100%, Specificity-99.3%),. The diagnostic titer for positive test is 10 iu/ml or a titer >1:100.
Group B. HIV/AIDS patients (ELISA positive/Western blot confirmed): 89 consecutive patients (82 men, 7 women, age group- 21 to 70 years) under our care were studied. Toxoplasma (IgG/IgM) antibodies were estimated in all at admission. In these patients, CDC criteria were applied to diagnose clinical cerebral toxoplasmosis and included:
1. Clinical features of CNS involvement.
2. Raised anti-toxoplasma IgG titers.
3. Typical CNS lesions on CT Scan/MRI.
4. The dramatic clinical response to the treatment within 3-5 days of anti-Toxoplasma therapy
After the initiation of conventional antitoxoplasma therapy repeat CT scan was done to document the radiological improvement within first 3 weeks. 5 patients could afford CD4+ count estimation.
Group C. 25 in patients (HIV seronegative; 12 men, 13 women) under our care for cerebral Tuberculoma/neurocysticercosis and who recovered with the appropriate antimycobacterial/ antiparasiticidal treatment comprised this group. Anti-toxoplasma IgG/IgM was done in all within 7 days of admission.
The seroprevalence in the adult immunocompetent population(Group A) was 30.9%(34% in men;26.2% in women) and this group exhibited the highest mean value of 376.8 i.u./ml (range:10-899) IgG in the entire study population. *The seroprevalence in patients with cerebral granuloma (Group C) was 28%; mean IgG: 21.4 i.u./ml(range:12-80). *The seroprevalence in HIV/AIDS was 67.8%. The mean IgG in asymptomatic was 111.5 i.u./ml(range:10-300 i.u./ml)*26/60 (43.3%) AIDS patients presented with cerebral Toxoplasmosis (REL-multiple:17, single-07, encephalitis-02). The mean IgG was 250 i.u./ml (range:12.5-340 i.u./ml)* 13/26 patients died within 3-12 days of admission(mean:7d)3 patients received anti-toxoplasma treatment(pre-death period 4, 5& 8 days). In the remaining 10 referred patients, diagnosis of cerebral toxoplasmosis was not considered in 6 at recent admission and readmission (within 3-4 weeks of discharge) in 4 by their treating physicians. All were receiving antituberculous treatment. It was too late for the antitoxoplasma drugs to give any benefit. The other 13 patients received anti-toxoplasma therapy. The clinical improvement was witnessed within 3-7 days and repeat CT scans demonstrated 75-100% clearance of the toxoplasmic lesions over 15-21 days.* Both women victims succumbed at 23 and 90 days of indoor stay despite complete resolution of toxoplasmic lesions. Similarly, a male with advanced AIDS succumbed at 21 days despite effective anti-toxoplasma therapy; but his CD4+ count was 43 cells/cmm. * CD4+ estimation in 5 patients ranged from 43-504 cells/cmm (mean=283.6). * 8/10 patients discharged on anti-toxo prophylaxis did not report for even 1st follow-up. 1 person was lost after 1st follow-up at 6 months; The last patient’s father reported his son’s death at 4 months after discharge.
Seroprevalence studies vary according to geographic location. The global seroprevalence is reported to be 46.1%. A study done in Delhi [Northern India] at National Institute of Communicable Diseases by Mittal V, Bhatia R and Sehgal S in 1990, reported an overall seroprevalence of only 1% in the 200 samples studied from the general population. We found much higher seroprevalence of Toxoplasmosis (30.9%-Mean titer: 352 iu/ml) in Mumbai (Western India) in the general population. A study by Jones et al in 9 United States (US) cities found that toxoplasma encephalitis in HIV-infected person varied by geographic area.
10-40% of adults with AIDS are seropositive for Toxoplasmosis in US. In Europe, Latin America and Africa where the incidence of latent toxoplasma infection is between 75-90%, number of AIDS patients who develop toxoplasmic encephalitis may be 3-4 times >US. The overall seroprevalence of Toxoplasmosis was found to be 67.4% in our HIV/AIDS patients. Thus, acquired primary Toxoplasma infection in Bombay seems to be subclinical; occurring between 0-30yr. Nonetheless, this seems to remain as a potential latent focus for reactivation of tissue Toxoplasmosis when the host immunity compromises. Therefore, with HIV infection, clinical recrudescence was witnessed by us between 21-40yr. The asymptomatic HIV patients with raised IgG showed a mean value of 111.5 i.u./ml(10-300 i.u./ml);but the mean IgG in the symptomatic patients with cerebral toxoplasmosis was 250 i.u/ml(120-300 i.u./ml) i.e. nearly 21/2 times the former group.
Toxoplasma encephalitis is reported to occur at <200 cells+high IgG titers =/>150 i.u./ml (France), <100 cells/ cmm (USA) and 35 times more common in those with CD4+ <50 cells/cmm(Edinburgh). The mean CD4+ count was 283.6 cells/cmm (range 43-504) in our 5 patients who could afford this test. Therefore, in India, the risk of cerebral toxoplasmosis seems to be higher even in moderately severe immunodeficiency. This risk observed by us was 43.3%(26/60). This is consistent with the study done in Norway which reported that of the 40 patients who had antitoxoantibodies, 18(45%) developed toxoplasma encephalitis;but this is higher than the risk of 25.4% observed in France and 30% in a study from Baltimore.
Hence, T. gondii has emerged as an important opportunistic infection in India but still the treatment is often delayed. We agree with Dunlop et al that there is an indication for primary prophylaxis in asymptomatic HIV patients with elevated antitoxoplasma IgG antibodies. We propose that estimation of anti-Toxoplasma IgG can be recommended as a screening test in all HIV-AIDS patients to detect latent infection. This may aid in advocating primary prophylaxis against Toxoplasmosis in clinically advanced AIDS in absence of CD4+ estimation. This may reduce the risk of Toxoplasmic encephalitis.
Anti-toxoplasma IgM was negative in entire study population-both healthy and immunocompromised as also reported in the literature. We also propose that estimation of IgM thus offers no additional benefit towards diagnosis or therapeutic intervention for Toxoplasmosis.
Part of the funding was met with from the Research Grant (code No. 19) sanctioned by The K.E.M. Hospital, Research Society for the year April 1997-March 1998
We are indebted to
1) Dr. (Mrs.) MS Bhattacharya, Head (Gynec. and Obst.) and Mrs. NN Desai, for the laboratory assistance
2) Mrs. Ray, Head, Blood bank, King Edward Memorial Hospital for providing sera for the control group.
3) Research Society, King Edward Memorial Hospital
[Table - 1], [Table - 2], [Table - 3]