Human pathology of Opisthorchis viverrini infection: a comparison of adults and children

The pathology of human opisthorchiasis in 22 adults (20 to 68 years) and 7 children (7 to 15 years) at autopsy is described. The changes of the liver in adults and children are similar and are summarized as follows: Enlargement of the liver was a common finding. Pericholangitis was observed in most cases. The pathology was confined to the large and medium-sized bile ducts where the flukes inhabited. The small interlobular bile ducts had minimal or unremarkable changes. Dilatation of the bile ducts with hyperplasia, desquamation and proliferation of the bile duct epithelial cells, glandular formation and fibrous connective tissue infiltration of the walls were the most common features. The pathological changes were well established within 7 to 15 years. Dilatation of the gallbladder, chronic cholecystitis and carcinoma were found only in adults. Eight of ten cases were cholangiocarcinoma and two were hepatocellular carcinoma.

Determination of quinine and quinidine in biological fluids by high performance liquid chromatography

A simple, specific, rapid and sensitive High Performance Liquid Chromatography (HPLC) method has been developed to measure plasma level of quinine and quinidine. The drugs were extracted successively from plasma at basic pH with chloroform and quantified on a revers-phase Z-module C18 HPLC column with fluorescence detector (excitation 340 nm, emission 425 nm). The isocratic mobile phase used was the mixture of 0.05 M ammonium formate and acetonitrile (93.5:6.5, v/v), adjusted pH to 2.0 with ortho-phosphoric acid. The limits of quantitation for these compounds were as low as 4 ng/ml of plasma, using a 0.25 ml specimen. Calibration curves were linear (R squared = 0.9994) in the range 0-7,000 ng/ml. An interassay reproducibility was 6.8%, 0.3% and 1.2% at the concentrations of 250 ng, 4,000 ng and 8,000 ng of quinine, respectively. Inter-assay coefficient of variation of quinidine was 1.8%, 2.7% and 3.7% at the concentrations of 250 ng, 1,500 ng and 3,000 ng, respectively. Recovery of quinine and quinidine were 76% and 81%, respectively. The method has been used in the analysis of quinine and quinidine in healthy volunteers receiving quinine or quinidine intravenously. The method is now being used to assay samples from field studies with satisfactory results.

A new intestinal fluke, Plagiorchis harinasutai n.sp

Dilution-sedimentation examination of stool specimens from four opisthorchiasis patients treated with praziquantel led to the discovery of six Plagiorchis worms. This is the first known report of plagiorchis infection in man in Thailand. The morphological features differed from those of previously described Plagiorchis species indicating that these worms belong to a new species, which we designated as Plagiorchis harinasutai n.sp. in honour of Professor Chamlong Harinasuta, former Dean of the Faculty of Tropical Medicine, Mahidol University, Bangkok. The holotype is held at the Museum and Reference Centre. Paratypes are held in the Bangkok School of Tropical Medicine, Faculty of Tropical Medicine, Mahidol University.

Determination of mefloquine in biological fluids using high performance liquid chromatography

A simple, specific and sensitive High Performance Liquid Chromatography (HPLC) method for determination of whole blood of mefloquine has been developed. WR 184806 was used as internal standard, using a two step extraction procedure followed by revers phase HPLC. Acetonitrile and dichloromethane were used as extraction solvents. Octanesulphonic acid was used as an ionpairing reagent. Detection of extracted mefloquine and internal standard was achieved at 222 nm. Calibration curves for mefloquine in whole blood showed linearity with correlation coefficients of 0.9999. The limitation of detection using a 1 ml sample was 50 ng/ml. Recovery of mefloquine varied from 61% to 81%. Due to the very similar behavior of the internal standard during extraction, changes in recovery are of minor importance. Good accuracy and precision were obtained (intra-assay coefficient of variation ranged between 1.8% and 5%; inter-assay coefficient of variation were less than 10% at 100 ng/ml and less than 6% at 1,000 ng/ml). The assay employs a rapid and simple two-step extraction which requires a small sample volume. The low limit of detection of mefloquine and the short retention time make the method suitable for routine analysis of mefloquine.

Electron microscopic study of phagocytosis in human spleen in falciparum malaria

The ultrastructure of the spleen of a patient who died of natural infection of Plasmodium falciparum was studied with emphasis on phagocytosis. Parasitized erythrocytes were shown to interact with the heterogenous populations of phagocytic cells. Phagocytosis occurred predominantly in macrophages than endothelial cells and immature forms of parasites were preferentially phagocytosed. Splenic trapping, pitting and destruction of both infected and noninfected erythrocytes were demonstrated. Other forms of interaction between phagocytic cells and parasitized erythrocytes observed include complex interdigitation, association of loose and tight phagosomes, and preferential sites of adherence, the significance of which need further investigation.

Development of in vitro microtest for the assessment of Plasmodium vivax sensitivity to chloroquine

An in vitro microtest to assess P. vivax sensitivity to chloroquine has been developed using a medium mixture which contained RPMI, Waymouth (GIBCO) and 15% (vol/vol) human serum group AB. The rate of success was highest in samples which were not washed by centrifugation before culturing in microtest plates predosed with varying concentrations of chloroquine. Evaluation of the effective concentration of chloroquine using a program for probit analysis of log dose/response test proved superior to simply using the percentage of schizont maturation.

The optimum dose of Puag-Haad in the treatment of taeniasis

Forty-two per cent of 24 patients with Taeniasis saginata were cured by two-gram dose of a crude aqueous extract of the wood Artocarpus lakoocha, Puag-Haad, while eighty per cent of 25 patients were cured by three-gram dose which is comparable to the results of five-gram dose but had less side-effect. Thus, the three-gram dose of Puag-Haad is recommended in the treatment of taeniasis.

Opisthorchis viverrini eggs and adult flukes as nidus and composition of gallstones

Three cases of opisthorchiasis with calculous cholecystitis was presented. The diagnosis of gallstones was made before praziquantel therapy in 2 cases, and 4 years after treatment in one case. The patients underwent cholecystectomy. Numerous O. viverrini eggs and one dead fluke were found in the bile in one case. A single stone was recovered from each gallbladder. All stones contained O. viverrini eggs. Fragments of flukes were also present in two cases. The stones consisted of a mixture of bilirubin pigment and calcium salts.

Incidence of bacteremia in patients with opisthorchiasis during recurrent cholangitis

A total of 257 haemocultures were performed in 50 patients with opisthorchiasis when they presented signs and symptoms of biliary tract infection. 19 patients showed positive haemoculture. There are no significant relationship between the age of the patient and the incidence of positive haemoculture. Septic shock occurred in 5 patients, one patient died. Out of 221 aerobic cultures, 14% were positive and of the 36 anaerobic cultures 11% were positive. The most common organism was Staphylococcus followed by Klebsiella and Bacillus spp. Anaerobic bacterias were Streptococcus spp. Clostridia spp. was not found in this study. Most organisms were sensitive to cefotaxime, cephalothin, kanamycin and chloramphenicol, and the least sensitive to ampicillin.

Inhibition of tolbutamide metabolism by antimalarial drugs

The effects of mefloquine (MQ), the combination of MQ with sulfadoxine-pyrimethamine (MSP), sulfadoxine (S), pyrimethamine (P) quinine (Q) and quinidine (Qd) on in vitro hepatic metabolism has been studied using tolbutamide as a substrate. The hydroxylation of tolbutamide was determined in the presence of variable concentrations of each compound. Tolbutamide hydroxylase activity in control microsomes was 0.20 +/- 0.13 nmole/min/mg microsomal protein at a substrate concentration of 150 microM. All compounds studied inhibited tolbutamide metabolism as shown by a decrease in 4-hydroxytolbutamide formation. The order of potency of the inhibitors was MSP greater than S greater than MQ greater than Q greater than Qd greater than P. MQ, MSP, S, Q, and Qd were examined in detail for the type of inhibition. MQ and Qd were non-competitive inhibitors, whereas MSP and S were competitive inhibitors and Q was an uncompetitive inhibitor of tolbutamide 4-hydroxylation. These data provide more information on the inhibitory potential of some antimalarial drugs on microsomal enzymes in human liver. S has been shown to be a potent inhibitor in vitro and this finding possibly explains the longer T 1/2 and MRT of MQ when co-administered with S in healthy volunteers. Further studies in man should be attempted in order to understand the clinical relevance of the inhibitory potential of the antimalarial drugs.

Effect of praziquantel treatment on antibody levels and lymphoproliferative responses in patients with opisthorchiasis

The purpose of this study was to explore alternative method(s) to monitor the efficacy of anthelmintic treatment of patients with opisthorchiasis. Therefore, in our initial attempt, we studied the changes in antibody levels and lymphoproliferative responses in O. viverrini infected patients before and 2 months after successful praziquantel treatment. The results showed that although a substantial reduction of the antibody levels occurred after such a treatment, it did not occur in all patients. In those showing reduction, the final level were still above 2 standard deviations of the normal mean value. The reduction was more profound for IgG antibody. With regard to the IgA antibody isotype, the reduction was not as marked. In contrast, IgE antibody levels in most patients not only failed to decline, but instead, showed a tendency to be elevated after praziquantel treatment. Unlike the antibody levels, there was no alteration in the lymphoproliferative response to PHA stimulation and therefore this parameter is not useful for our intended objective. It was suggested that studies of a more specific O. viverrini component may be more reliable than the current method of parasitological examination of eggs in the feces of suspected individuals.

Detection of antibodies against Opisthorchis viverrini in patients before and after treatment with praziquantel

Levels of antibody in sera of 78 patients with opisthorchiasis, 30 patients with other liver diseases, 10 patients with schistosomiasis and 30 healthy individuals were compared using three serodiagnostic tests, namely indirect haemagglutination (IHA), enzyme-linked immunosorbent assay (ELISA) and lectin immuno test (LIT). The geometric mean reciprocal titer in sera of opisthorchiasis patients was significantly higher than patients with other diseases, patients with schistosomiasis and healthy individuals (p less than 0.00001). After treatment with praziquantel, the antibody titers were decreased and became lowest 120 days after treatment. A statistically significant decrease from the pre-treatment sample was observed only at 120 days after infection and not earlier and only with ELISA (p = 0.03) and not with IHA and LIT (p greater than 0.05). Even with ELISA, significant decrease in antibody titer was apparent only when the pre-treatment sera had high enough antibody titer. ELISA was therefore better than the other two tests for the assessment of cure provided that the titer of pre-treatment sera was high.

Characterization of humoral immune response in the serum and bile of patients with opisthorchiasis and its application in immunodiagnosis

The humoral immune response in patients with opisthorchiasis was investigated using an enzyme-linked immunosorbent assay. IgG antibody reactive with Opisthorchis viverrini antigens was present in the serum of all patients. The infection also stimulated specific IgA and IgE antibody responses in most patients and, in practically all patients, there was a marked increase of total IgE. There was a moderate but significant correlation between serum IgG antibody level and severity of infection as judged from the quantity of eggs in the stool of the patients. There was also a significant elevation of antibody in the bile and serum of O. viverrini-infected patients who also had biliary obstruction. Analysis of paired samples from individual patients showed that while IgG was the predominant class of antibody in the serum of all patients, IgA was present at approximately the same level as IgG or higher in the bile of many patients. In addition to IgA and IgG antibodies, IgE antibody was also detectable in 50% of the bile samples. The high level of IgA antibody in the bile together with its presence in association with the secretory component suggested a selective transport and/or local production of IgA antibody by the hepatobiliary system of these patients.

Analysis of Opisthorchis viverrini antigens by immunoprecipitation and polyacrylamide gel electrophoresis

Antigenicity of adult Opisthorchis viverrini, metacercariae and eggs was investigated by radio-immunoprecipitation and polyacrylamide gel electrophoresis using sera from patients with opisthorchiasis and from hamsters experimentally infected with O. viverrini metacercariae. 125I-labelled aqueous somatic extract and in vitro metabolic products of adult worms, and the extracts of metacercariae and eggs were immunoprecipitated, electrophoresed and autoradiographed and major antigens were characterized. Although components with Mr of greater than 116, 89, 78 and 20 kD appeared to be specifically associated with the somatic extract of adult fluke, the 89 kD protein was the most prominent component found in the in vitro culture fluid of adult worms and the metacercarial extract. Hamsters, experimentally infected with O. viverrini, also showed the presence of antibody reactive with the 89 kD component within 15 days of infection. The potential of this antigen in immunodiagnosis is discussed.

The hyaluronidase activities of some Southeast Asian snake venoms

The hyaluronidase activities of venoms of snakes indigenous to Southeast Asia were investigated. With the exception of the venom of the Malayan krait Bungarus candidus, the elapid venoms had either little or no hyaluronidase activities, whereas the viperid venoms possessed considerable activity. A component of Russell's viper venom with hyaluronidase activities had a mol. wt of approximately 14,000. Neither MP4, a monoclonal antibody raised against the purified Russell's viper venom hyaluronidase toxin, nor a monospecific polyclonal antivenom neutralized the hyaluronidase activities of this purified hyaluronidase component of crude Russell's viper venom. The Russell's viper venom hyaluronidase activities was labile on heating and storage. The significance of these observations to envenomation and antivenom production is discussed.

A comparison of the pharmacokinetics of mefloquine in healthy Thai volunteers and in Thai patients with falciparum malaria

We have studied the kinetics of a single oral dose of mefloquine (750 mg) in 12 Thai patients with falciparum malaria and have compared the results with those of a previous study in 12 healthy Thai volunteers. All the patients responded to treatment with a mean parasite clearance time of 66.6 h and a mean fever clearance time of 54.1 h. There was no significant difference in peak plasma concentration, time to peak, area under the curve or apparent volume of distribution between patients and controls. However, the terminal half-life (t1/2) and mean residence time (MRT) were shorter in the patients (12.2 vs 16.7 days for t1/2 and 15.5 vs 21.4 days for MRT). We conclude that there are changes in the disposition of mefloquine related to malaria, although the exact basis of the changes is not clear.

Spleen in falciparum malaria: ultrastructural study

An ultrastructural study was undertaken of the spleen of 13 year-old-boy who died of falciparum malaria. The spleen revealed the following: both parasitized and non-parasitized erythrocytes are phagocytosed in large numbers by macrophages, littoral and reticular cells. Blood congestion and trapping of parasitized erythrocytes are commonly seen in splenic sinusoids and cords. Erythrocytes forming rosette structure around immuno-presenting cells is observed. The results of this study provide evidence that the mechanisms underlying splenic host defence in malaria include both immunological and non-immunological interaction with erythrocytes. Splenic trapping of parasitized erythrocytes is an important defence mechanism and the phagocytosis of erythrocytes probably accounts for anaemia.

Subcutaneous phycomycosis mimics elephantiasis

A case of subcutaneous phycomycosis involving the right thigh for 1 year duration which mimic elephantiasis was reported in a 21-year-old military man. An initial diagnosis was that of a subcutaneous tissue lesion attributed to parasitic manifestation but turned out to be that of subcutaneous fungal infection both clinically and histologically. The lesion was successfully treated with cotrimoxazole for a period of one month, and followed up for 4 1/2 months with complete cure.

High rate of Plasmodium vivax relapse following treatment of falciparum malaria in Thailand

Within two months of treatment for falciparum malaria, Plasmodium vivax infections developed in 58 (33%) of 174 patients who had received a quinine or quinidine regimen and in 46 (32%) of 145 patients who had received mefloquine with inpatient follow-up of more than six weeks. The time to vivax relapse was significantly longer after mefloquine treatment (median 47 days, range 30-65) than after quinine or quinidine treatment (21 days, 15-36; p less than 0.0001). All patients remained outside areas of malaria transmission. These findings suggest a very high rate of double infection in Thailand with acute suppression of vivax by falciparum malaria, and warrant evaluation of radical therapy with primaquine in certain patients with acute falciparum malaria.

Dynamic alteration in splenic function during acute falciparum malaria

Plasmodium-infected erythrocytes lose their normal deformability and become susceptible to splenic filtration. In animal models, this is one mechanism of antimalarial defense. To assess the effect of acute falciparum malaria on splenic filtration, we measured the clearance of heated 51Cr-labeled autologous erythrocytes in 25 patients with acute falciparum malaria and in 10 uninfected controls. Two groups of patients could be distinguished. Sixteen patients had splenomegaly, markedly accelerated clearance of the labeled erythrocytes (clearance half-time, 8.4 +/- 4.4 minutes [mean +/- SD] vs. 62.5 +/- 36.5 minutes in controls; P less than 0.001), and a lower mean hematocrit than did the patients without splenomegaly (P less than 0.001). In the nine patients without splenomegaly, clearance was normal. After institution of antimalarial chemotherapy, however, the clearance in this group accelerated to supernormal rates similar to those in the patients with splenomegaly, but without the development of detectable splenomegaly. Clearance was not significantly altered by treatment in the group with splenomegaly. Six weeks later, normal clearance rates were reestablished in most patients in both groups. We conclude that splenic clearance of labeled erythrocytes is enhanced in patients with malaria if splenomegaly is present and is enhanced only after treatment if splenomegaly is absent. Whether this enhanced splenic function applies to parasite-infected erythrocytes in patients with malaria and has any clinical benefit will require further studies.

Two-site immunoradiometric assay for detection of Plasmodium falciparum antigen in blood using monoclonal and polyclonal antibodies

Three systems of immunoradiometric assays (IRMAs), a two-site monoclonal antibody sandwich IRMA (MAb-IRMA), two-site polyclonal antibody-monoclonal antibody sandwich IRMA (PAb-MAb-IRMA), and two-site polyclonal antibody sandwich IRMA (PAb-IRMA), were developed to detect low-grade infections with Plasmodium falciparum. The assays showed good correlation with parasitemia when tested against parasites from in vitro cultures (r = 0.996, 0.994, and 0.998 for MAb-, PAb-MAb-, and PAb-IRMA, respectively), with the ability to detect as few as 0.24, 0.67, and 1.82 parasites per 10(7) erythrocytes, respectively. The assays were specific for P. falciparum, since a serially diluted specimen from a patient with vivax malaria with an initial parasitemia of 0.8% and almost all of the undiluted specimens from five other vivax malaria patients were negative. The assays were performed on patients with falciparum malaria before and after treatment with antimalarial drugs. Before treatment, all 24 patients were positive by all three systems of two-site sandwich IRMAs. Two weeks after treatment, 81.8% (18 of 22) of the patients were positive by microscopic examination, but the IRMA positivity rates were 90.9% (20 of 22), 86.4% (19 of 22), and 81.8% (18 of 22) for MAb-, PAb-MAb-, and PAb-IRMA, respectively. Four weeks after treatment, all 19 patients were negative by microscopic examination, but 52.6% (10 of 19) of the patients were still positive with MAb- and PAb-MAb-IRMA and 31.6% (6 of 19) were positive with PAb-IRMA. Comparison between the three systems of IRMA showed that the MAb-IRMA was superior to the other two systems for three reasons. First, it gave a lower count when tested with blood from healthy individuals. Second, it gave a higher count when tested with blood from patients with falciparum malaria. Third, it gave better correlation with parasitemia when blood from falciparum malaria patients was tested. MAb-IRMA is recommended for use for the detection of low-grade P. falciparum infection.

Flunarizine and verapamil inhibit chloroquine-resistant Plasmodium falciparum growth in vitro

Using pharmacological properties in relation to the biochemistry of P. falciparum, verapamil, flunarizine, and chlorpromazine which are calcium blockers were selected to test for their antimalarial activity against P. falciparum in vitro. Results revealed that the drugs inhibited parasite population growth in the following order of IC50: verapamil 1 X 10(-6) M, chlorpromazine 3.5 X 10(-6) M, and flunarizine 5 X 10(-6) M. These three calcium blockers have antimalarial effects on chloroquine resistant parasite (alone T9/94) but are less potent when compared with the efficacy of quinine or mefloquine in vitro.