Factors contributing to fatal snake bite in the rural tropics: analysis of 46 cases in Thailand.

Records of 46 cases of fatal bites by identified snakes from 15 provincial hospitals throughout Thailand contained sufficient information for detailed analysis. Bungarus candidus and Calloselasma rhodostoma were each responsible for 13 deaths, Naja kaouthia for 12, Vipera russelli for 7 and B. fasciatus for one. Major causes of death among elapid victims were respiratory failure (26) and complications of prolonged mechanical ventilation (10), and among viper victims shock (12), intracranial haemorrhage (9), complications of local wound necrosis (7) including tetanus (2), and renal failure (2). Factors contributing to fatal outcome included inadequate dose of antivenom (15 cases), misidentification of the snake leading to use of the wrong antivenom (12), problems associated with mechanical ventilation (10), and delayed arrival in hospital after traditional (herbal) treatment (10). Similar problems have been identified in other tropical countries. Education of medical staff and the patient population at highest risk could reduce snake bite mortality

ELISA confirmation of acute and past envenoming by the monocellate Thai cobra (Naja kaouthia).

The monocellate Thai cobra (Naja kaouthia) is a major cause of snake bite mortality and morbidity throughout Thailand, but neither the local nor the systemic effects of its venom are diagnostic. Species diagnosis is important because only monospecific antivenoms are available for treatment in Thailand. We tested the ability of the ELISA technique to detect venom antigen in the sera of 58 acute snake bite cases including 4 fatalities, and venom antibody in 51 patients bitten between 1 month and 19 years previously. N. kaouthia venom antigen was found in 8 of 33 patients with only local envenoming and in 14 of 20 with local plus systemic (neurotoxic) envenoming, but the mean venom concentration was 33 times greater in the latter group. The serum of 1 fatal case contained banded krait (Bungarus fasciatus) but no cobra venom antigen. N. kaouthia venom antibody was present in sera of patients bitten between 1 month and 7 years previously. Antibody was found in 6 of 8 patients who had had local envenoming alone but in only 19 of 41 who had had systemic envenoming treated by antivenom. The titer of antibody declined with an approximate half time of 2-3 years. One patient had a significant titer of B. fasciatus venom antibody. This study confirms the value of ELISA-immunodiagnosis and the predominance of N. kaouthia as a cause of neurotoxic envenoming in the Bang Phli area. However, the attribution of 1 fatal case to B. fasciatus bite suggests that patients with neurotoxic signs should be given B. fasciatus antivenom if they fail to respond to cobra antivenom

Antimalarial effects of rifampin in Plasmodium vivax malaria.

The antimalarial effects of rifampin in 60 adults with Plasmodium vivax malaria were assessed. There were three treatment groups: rifampin (20 and 15 mg/kg of body weight per day for 1 and 4 days, respectively; n = 5); rifampin followed by primaquine (15 mg of base per day for 14 days; n = 25), and chloroquine (25 mg of base per kg over 3 days) followed by primaquine (n = 30). All patients were hospitalized till clearance of fever and parasites, and 45 patients stayed in the hospital for 1 month. Despite initial clearance of fever in all patients and a > or = 6-fold reduction in parasitemia per 48-h life cycle, rifampin alone was not effective: all five patients had subsequent R2-like parasitological responses. All patients treated with rifampin-primaquine cleared both fever and parasitemia, but the therapeutic responses were slower than those following treatment with chloroquine-primaquine. Final fever clearance times were significantly longer (mean [standard deviation] = 43 [35] versus 27 [19] h; P = 0.046), and the parasite clearance times (to 50 and 90% of admission parasite counts and to a level undetectable in a peripheral blood smear) were also significantly greater (P = 0.053 to < 0.001). However, reappearance of infection occurred in only one patient treated with rifampin-primaquine. The results of this study suggest that rifampin at the usual therapeutic doses has partial activity against blood stages of P. vivax in humans but that used alone it is insufficient for cure. Rifampin might therefore be of value in combination antimalarial therapy

Antimalarial effects of rifampin in Plasmodium vivax malaria.

The antimalarial effects of rifampin in 60 adults with Plasmodium vivax malaria were assessed. There were three treatment groups: rifampin (20 and 15 mg/kg of body weight per day for 1 and 4 days, respectively; n = 5); rifampin followed by primaquine (15 mg of base per day for 14 days; n = 25), and chloroquine (25 mg of base per kg over 3 days) followed by primaquine (n = 30). All patients were hospitalized till clearance of fever and parasites, and 45 patients stayed in the hospital for 1 month. Despite initial clearance of fever in all patients and a > or = 6-fold reduction in parasitemia per 48-h life cycle, rifampin alone was not effective: all five patients had subsequent R2-like parasitological responses. All patients treated with rifampin-primaquine cleared both fever and parasitemia, but the therapeutic responses were slower than those following treatment with chloroquine-primaquine. Final fever clearance times were significantly longer (mean [standard deviation] = 43 [35] versus 27 [19] h; P = 0.046), and the parasite clearance times (to 50 and 90% of admission parasite counts and to a level undetectable in a peripheral blood smear) were also significantly greater (P = 0.053 to < 0.001). However, reappearance of infection occurred in only one patient treated with rifampin-primaquine. The results of this study suggest that rifampin at the usual therapeutic doses has partial activity against blood stages of P. vivax in humans but that used alone it is insufficient for cure. Rifampin might therefore be of value in combination antimalarial therapy

Prediction, prevention, and mechanism of early (anaphylactic) antivenom reactions in victims of snake bites.

Victims of snake bites are often subjected to cutaneous or conjunctival hypersensitivity testing before being given antivenom. None of 12 early (anaphylactic) reactions was predicted by these tests in 25 Nigerian and Thai patients. The incidence and severity of early reactions was the same whether antivenom was given by intravenous injection over 10 minutes or diluted and given as an intravenous infusion over 30 minutes. Although antivenom activated complement in vitro, there was no evidence of complement activation or formation of immune complexes in patients bitten by snakes who were treated with antivenom, whether or not they developed early reactions. Higher doses of antivenom might induce the complement activation and formation of immune complexes (aggregates) that have been observed during the clinically more severe reactions associated with homologous immunoglobulin treatment

Detection of venom by enzyme linked immunosorbent assay (ELISA) in patients bitten by snakes in Thailand.

The ability of an enzyme linked immunosorbent assay (ELISA) to detect venom was evaluated in 251 patients bitten by four of the commonest poisonous snakes in Thailand. Serum was tested only from patients who brought the snakes that had bitten them. About one third of all bitten patients had detectable venom antigenaemia, though a smaller proportion were symptomatic. Serum venom concentrations on admission correlated with the severity of clinical manifestations. The test was sensitive and specific even for specimens that had been collected and stored under suboptimal conditions. The technique is suitable for forensic use in cases of suspected snakebite. The combination of snake identification and venom antigen detection should be a more reliable means of studying the epidemiology of snakebite than the measurement of venom antibodies in a population

Detection of venom by enzyme linked immunosorbent assay (ELISA) in patients bitten by snakes in Thailand.

The ability of an enzyme linked immunosorbent assay (ELISA) to detect venom was evaluated in 251 patients bitten by four of the commonest poisonous snakes in Thailand. Serum was tested only from patients who brought the snakes that had bitten them. About one third of all bitten patients had detectable venom antigenaemia, though a smaller proportion were symptomatic. Serum venom concentrations on admission correlated with the severity of clinical manifestations. The test was sensitive and specific even for specimens that had been collected and stored under suboptimal conditions. The technique is suitable for forensic use in cases of suspected snakebite. The combination of snake identification and venom antigen detection should be a more reliable means of studying the epidemiology of snakebite than the measurement of venom antibodies in a population

Magnetic resonance imaging of the brain in patients with cerebral malaria.

In a prospective study of cerebral malaria, 24 adults with this disease underwent magnetic resonance imaging (MRI) of the brain. Four patients died. Two of these patients (nos. 17 and 24) had breathing abnormalities requiring ventilatory support followed by clinical signs of brain death. Four days later MRI of patient 17 showed gross swelling of the brain, and 5 hours later MRI of patient 24 showed foramen magnum herniation. Twenty-two patients had no evidence of cerebral edema, but MRI revealed that brain volume during acute cerebral malaria was slightly greater than that during the convalescent phase of the disease. This difference was attributed to an increase in the volume of intracerebral blood. The cerebral volume was lower during early convalescence than several months later. The volume of the brain in patients with cerebral malaria is increased. This increased volume probably results from sequestration of parasitized erythrocytes and compensatory vasodilatation rather than from edema. Brain stem herniation may occur, but its temporal relation to brain death in cases of cerebral malaria remains uncertain

A national hospital-based survey of snakes responsible for bites in Thailand.

Snakes which had been killed and brought to hospital with the patients they had bitten were collected in 80 district and provincial hospitals throughout 67 provinces in Thailand in order to establish the geographical distribution and relative medical importance of the venomous species. Of the 1631 snakes collected, 1145 were venomous: Malayan pit vipers (Calloselasma rhodostoma), green pit vipers (Trimeresurus albolabris) and Russell's vipers (Daboia russelii) were the most numerous, while T. albolabris, C. rhodostoma and spitting cobras ('Naja atra') were the most widely distributed. In 22 cases, non-venomous species were mistaken for venomous ones and antivenom was used unnecessarily. The Malayan krait (Bungarus candidus) was confused with B. fasciatus in 5 cases and B. fasciatus antivenom was used inappropriately. The study extended the known ranges of most of the medically-important venomous species in Thailand. Correct identification of venomous snakes is especially important in Thailand because the locally-produced antivenoms are monospecific. The technique of hospital-based collection, labelling and preservation of dead snakes brought by bitten patients is recommended when rapid assessment of a country's medically important herpetofauna is required