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Aims—To determine whether IgG immunoblotting can improve the diagnosis of ocular toxoplasmosis. Methods—Samples of serum were tested from patients with ocular lesions that could be caused by toxoplasmosis. All such samples from Scotland and Northern Ireland are usually referred to the Scottish Toxoplasma Reference Laboratory. From questionnaires filled out by the clinicians, two groups of sera were identified: ocular toxoplasmosis (active and quiescent), n = 54 (group 1); and eye disease as a result of other causes, n = 36 (group 2). Control groups were made up of sera from patients with no eye disease and a normal dye test result (≤ 125 IU/ml), n = 16 (group 3); and toxoplasma seronegative, cytomegalovirus (CMV) positive, and herpes simplex virus (HSV) positive sera (group 4), n = 18. Results—Immunoblots with an active pattern could be identified (IgG antibodies against at least four antigens with molecular weight of 6, 20, 22, 23, 25, and 36 kDa). Significantly more of this pattern was found in group 1 (33 of 54; 61.1%) compared with group 2 (nine of 36; 25%) or group 3 (six of 16; 37.5%). Within group 1, significantly more sera with an active pattern had dye test results ≥ 65 IU/ml compared with those without. More sera from patients < 30 years of age were found with the active pattern in group 1 compared with group 2. No group 4 sera had active immunoblot patterns. Conclusions—The immunoblot result adds more support to the diagnosis of ocular toxoplasmosis. In cases where the clinical diagnosis is difficult, immunoblots are particularly indicated; if negative, other causes of eye disease should be sought.

Different ways of eluting IgG antibodies against Toxoplasma gondii from blood spots on PKU filter papers from newborns were examined, and the eluate was analysed by Enzyme Immunosorbent Assay (EIA). 10-mm diameter discs (method A), and 3-mm discs (method B) were eluted overnight, and 3-mm discs were eluted directly for 2 hours in the EIA wells (method C). Two groups of paired samples were tested: blood spots on the PKU card from the newborn, cord blood, and a venous blood sample from the mother collected shortly after delivery (Group 1, 191 samples); or PKU cards from the newborns and serum collected from the mother during the first trimester (Group 2, 426 samples). The best results were found for Group 1; method A, a sensitivity of 100% (63/63), and a specificity of 100% (128/128) (r = 0.934, P < 0.0001), and for Group 2; method C, a sensitivity of 100% (125/125), and a specificity of 100% (301/301) (r = 0.822, P < 0.0001). When method C, was used on 188 samples stored for 16-18 month at -20 degrees C, a sensitivity of 100% (62/62) and a specificity of 99.2% (125/126) (r = 0.913, P < 0.0001) were found. The PKU filter paper method is reliable and reproducible, and can be used in screening projects based on analysis of neonatal samples, and in epidemiological studies on toxoplasmosis in pregnant women.

The fluorescent antibody technique first described by CooNs, CREECH and J o ~ s (1961) has been widely used for the detection of antigen and antibody in numerous systems including infectious diseases where it has found its widest and most important use from a public health standpoint. BOZFMAN and ELISBERG (1963 and 1967) applied the technique to the serological diagnosis of scrub typhus and their procedures are now being used in laboratories throughout the world. The technique described by them is one of the most reliable serological tests known; however, it requires collection of a volume of whole blood which is not always possible in epidemiological work or in small mammals. Other workers have encountered similar problems with other diseases and ANDERSON, Sta)trN and WILLIAMS (1961) reported on a method that used dried whole smears on filter paper in the fluorescent antibody test for the diagnosis of schistosomiasis. More recently, BAILEY, CUNNINGHAM and KIM~ER (1967) reported on the same technique adapted for a study of trypanosomiasis in Africa which Walton and Arjona reported on its adaption for use in the indirect fluorescent antibody test for toxoplasmosis. This paper reports on the combination of these two techniques for the detection and titration of antibodies against the causative agent of scrub typhns--R, tsutsugamushi.