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Background: Artemisinin-based combination therapy (ACT) is recommended as a means of prolonging the effectiveness of first-line malaria treatment regimens. Different brands of mefloquine (MQ) have been reported to be non-bioequivalent; this could result in sub-therapeutic levels of mefloquine with decreased efficacy. In 2002, mefloquine-artesunate (MQ-AS) combination therapy was adopted as the first-line treatment for uncomplicated Plasmodium falciparum malaria in the Amazon region of Peru. Although MQ resistance has yet to be reported from the Peruvian Amazon, it has been reported from other countries in the Amazon Region. Therefore, continuous monitoring is warranted to ensure that the first-line therapy remains efficacious. This study examines the in vivo efficacy and pharmacokinetic parameters through Day 56 of three commercial formulations of MQ (Lariam, Mephaquin, and Mefloquina-AC Farma) given in combination with artesunate., Methods: Thirty-nine non-pregnant adults with P. falciparum mono-infection were randomly assigned to receive artesunate in combination with either (1) Lariam, (2) Mephaquin, or (3) Mefloquina AC. Patients were assessed on Day 0 (with blood samples for pharmacokinetics at 0, 2, 4, and 8 hours), 1, 2, 3, 7, and then weekly until day 56. Clinical and parasitological outcomes were based on the standardized WHO protocol.Whole blood mefloquine concentrations were determined by high-performance liquid chromatography and pharmacokinetic parameters were determined using non-compartmental analysis of concentration versus time data., Results: By day 3, all patients had cleared parasitaemia except for one patient in the AC Farma arm; this patient cleared by day 4. No recurrences of parasitaemia were seen in any of the 34 patients. All three MQ formulations had a terminal half-life of 14-15 days and time to maximum plasma concentration of 45-52 hours. The maximal concentration (Cmax) and interquartile range was 2,820 ng/ml (2,614-3,108) for Lariam, 2,500 ng/ml (2,363-2,713) for Mephaquin, and 2,750 ng/ml (2,550-3,000) for Mefloquina AC Farma. The pharmacokinetics of the three formulations were generally similar, with the exception of the Cmax of Mephaquin which was significantly different to that of Lariam (p = 0.04)., Conclusion: All three formulations had similar pharmacokinetics; in addition, the pharmacokinetics seen in this Peruvian population were similar to reports from other ethnic groups. All patients rapidly cleared their parasitaemia with no evidence of recrudescence by Day 56. Continued surveillance is needed to ensure that patients continue to receive optimal therapy.

In 2001, Peru changed its treatment policy for uncomplicated Plasmodium falciparum malaria on the northern Pacific Coast to sulfadoxine-pyrimethamine with atresunate (SP-AS). Because Peru was the first country in the Americas to adopt this combination therapy, we established a surveillance system in the region to assess the frequency of new or worsening symptoms after starting therapy. Over a period of two years, 1,552, or approximately two-thirds of all patients with uncomplicated P. falciparum malaria who had received SP-AS on the northern coast were followed up. Of these, 8.8% reported at least one adverse effect, with the most common being vomiting, nausea, headache, abdominal pain, dizziness, and fever; no severe adverse effects related to SP-AS therapy were identified. Treatment of uncomplicated malaria with SP-AS was associated with a low frequency of mild adverse effects in Peru, and therefore should be considered as a first-line therapy in areas of the Americas where SP efficacy is still high.

A strain of Plasmodium falciparum from Peru was adapted to splenectomized Aotus nancymaae and Aotus vociferans monkeys. The Peru 134/CDC strain of P. falciparum was shown to be resistant to treatment with chloroquine in monkeys and partially resistant to mefloquine and malarone. Genetic mutations in crt, dhfr, dhps, and cytochrome b genes conferring drug resistance were also determined for this Peruvian strain of P. falciparum.

High levels of Plasmodium falciparum resistance to both chloroquine (CQ) and sulfadoxine-pyrimethamine (SP) have been documented throughout the Amazon Basin of South America. Because of reports about the persistent efficacy of both of these drugs in the northwestern Peruvian Amazon region, we carried out an evaluation of the therapeutic efficacy of chloroquine (25 mg/kg) and SP (25 mg/kg of the sulfadoxine component) for the treatment of uncomplicated P. falciparum infections at two sites: Ullpayacu and Pampa Hermoza/Alianza. A total of 111 patients were enrolled. Only 5 (14.3%) of the 35 patients who received CQ had an adequate clinical and parasitologic response (ACPR). Six subjects (17%) had early treatment failure, 1 (2.9%) had late clinical failure, and 23 (65.7%) had late parasitologic failure (LPF). Of the subjects treated with SP, 92.3% had ACPR and 7.7% had LPF. Based on these findings, it is clear that there are at least limited areas within the Peruvian Amazon region where P. falciparum strains continue to be sensitive to SP.

To assist the Peruvian Ministry of Health in modifying the malaria treatment policy for their north Pacific coastal region, we conducted an in vivo efficacy trial of sulfadoxine-pyrimethamine (SP) and SP plus artesunate (SP-AS) for the treatment for uncomplicated Plasmodium falciparum infections. A total of 197 patients were randomized to therapy with either SP (25 mg/kg of the sulfadoxine component in a single dose on day 0) or a combination of SP plus AS (4 mg/kg on days 0, 1, and 2) and were followed for 28 days for symptoms and recurrence of parasitemia. No statistically significant differences between the two groups were observed on enrollment with respect to age, sex, history of malaria, or geometric mean parasite density. A total of 185 subjects completed the 28-day follow-up. Of the 91 subjects treated with SP alone, two had recurrences of parasitemia on day 7 and one on day 21. Of the 94 subjects treated with SP-AS, one had a recurrence of parasitemia on day 21. Fever and asexual parasite density decreased significantly more rapidly and the proportion of patients with gametocytemia on days 3-28 was significantly lower in subjects treated with combination therapy than in those who received SP alone. No severe adverse drug reactions were observed; however, self-limited rash and pruritus were significantly more common and an exacerbation of nausea, vomiting, and abdominal pain were observed significantly more frequently among patients who had received SP-AS. These results have contributed to a National Malaria Control Program decision to change to SP-AS combination therapy as the first-line treatment for uncomplicated P. falciparum malaria in northern coastal Peru in November 2001, making Peru the first country in the Americas to recommend this combination therapy.

In vivo antimalarial drug efficacy studies of uncomplicated Plasmodium falciparum malaria at an isolated site in the Amazon basin of Peru bordering Brazil and Colombia showed >50% RII/RIII resistance to sulfadoxine-pyrimethamine but no evidence of resistance to mefloquine.

Between 1998 and 2001, the Peruvian Ministry of Health made sweeping changes in its malaria treatment policies in response to a resurgence of disease and the spread and intensification of antimalarial drug resistance. On the Pacific Coast, the first-line treatment for uncomplicated Plasmodium falciparum malaria was changed to combination therapy with sulfadoxine-pyrimethamine plus artesunate; in the Amazon region, mefloquine-artesunate combination therapy was introduced. With these changes in treatment policy, Peru became the first country in the Americas to use combination therapy with an artemisinin drug as its first-line treatment for falciparum malaria and the first country in the world to use two different drug combination therapy regimens based on an artemisinin drug in different regions of the country. This paper describes the process involved in assessing the geographic distribution and intensity of antimalarial drug resistance throughout the country and the use of that information to guide decisions related to national malaria treatment policy.

Reports from several sites in South America suggest the presence of isolated cases of chloroquine-resistant Plasmodium vivax malaria. To investigate the possibility of chloroquine-resistant P. vivax in Peru, we conducted 28-day in vivo drug efficacy trials at three sites in the Amazon region and one site on the northern Pacific Coast between 1998 and 2001. A total of 242 patients between the ages of 2 and 60 years were enrolled (177 from the Amazon region and 65 from the northern coast). All subjects received directly observed therapy with chloroquine, 25 mg/kg, over a three-day period. On enrollment, 49% had a documented fever and 96% had a history of fever; their geometric mean parasite density was 5,129 parasites/microL. A total of 212 (88%) of the 242 subjects completed their 28-day follow-up. Four of the 177 patients from the Amazon region had a recurrence of P. vivax parasitemia on days 21 and 28 after treatment was initiated. Two of these patients had chloroquine-resistant infections, based on polymerase chain reaction-single-stranded conformational polymorphism genotyping and chloroquine-desethylchloroquine blood levels, which were > or = 97 ng/mL at the time of the reappearance of parasitemia. None of the subjects studied on the northern Pacific Coast had recurrent parasitemia.

In the Amazon Basin of Peru, more than 50% of patients with uncomplicated Plasmodium falciparum malaria fail to respond to treatment with chloroquine or sulfadoxine-pyrimethamine. To assist the National Malaria Control Program in identifying an alternative first-line therapy for this region, we conducted a trial of the safety and efficacy of mefloquine (MQ) compared with mefloquine-artesunate (MQ-AS) combination therapy. Patients with uncomplicated P. falciparum infections between the ages of 5 and 50 years were randomly assigned to be treated with either MQ (15 mg/kg in a single oral dose) or MQ (15 mg/kg) plus AS (4 mg/kg/day for three days). A total of 98 patients were enrolled and followed for 28 days. None of the 47 patients who received MQ alone or the 51 patients who received MQ-AS combination therapy had recurrences of parasitemia during the 28-day follow-up period. Asexual parasite densities decreased significantly more rapidly and the proportion of patients with gametocytes was significantly lower on days 3-21 in the MQ-AS group than in patients treated with MQ alone. All patients tolerated the medication well. Based on the results of this study and with the objective of slowing the development of resistance, the Peruvian Ministry of Health has decided to revise its malaria treatment policy and recommend combination therapy with MO-AS as the new first-line treatment of uncomplicated P. falciparum malaria in the Amazon region.

The World Health Organization (WHO) has developed guidelines for in vivo antimalarial drug efficacy testing for Plasmodium falciparum and Plasmodium vivax in areas with low-to-moderate transmission, such as the Americas. These guidelines are used widely by ministries of health and national malaria control programs to assess the efficacy of their first-line and second-line drugs for the treatment of malaria and to provide the information necessary to update national malaria treatment policies. Following the WHO guidelines, we have conducted in vivo efficacy trials with a variety of drugs and drug combinations against P. falciparum and P. vivax at 13 sites in Peru, Bolivia, and Ecuador. Based on these experiences, we have identified several modifications that we believe should be made in the WHO recommendations to make them more suitable to the relatively low levels of P. falciparum transmission in the Americas and to the logistic challenges of carrying out such studies in sparsely populated areas, such as the Amazon Basin. These include changes in inclusion and exclusion criteria, in enrollment and follow-up procedures, and in the measurement of study outcomes.

In spite of increasing resistance, chloroquine remains the primary drug for treatment of malaria in most sub-Saharan African countries. We evaluated the effect of drug treatment policy on the case-fatality rates of children, adjusting for differing distributions of malaria and severe anemia. In 1991, 63% of children were treated with chloroquine while the remaining 37% were treated with a regimen that would eliminate and clear parasitemia. Case-fatality rates were 13% and 4.1%, respectively; the proportion of deaths attributable to chloroquine treatment was 69%. The trend in case-fatality rates for malaria decreased as an increasing proportion of children received an effective treatment regimen; adjusted malaria case-fatality rates were 5.1%, 3.6%, and 3.3% in 1992, 1993, and 1994, respectively, when 85% of children in 1992 and 97% of children in 1993-1994 received effective therapy. These 4 years of data provide strong evidence that continued use of chloroquine in areas with resistance is contributing to excess Plasmodium falciparum-related deaths.

As part of an effort to assess antimalarial drug resistance in Peru, we carried out 14-day in vivo efficacy trials of chloroquine (CQ; 25 mg/kg) and sulfadoxine-pyrimethamine (SP; 25 mg/kg of the sulfadoxine component) for the treatment of uncomplicated Plasmodium falciparum infections at three sites on the northern coast of Peru. Mefloquine (MQ; 15 mg/kg) also was evaluated at one site. The results from all three sites were similar. Of the 53 patients treated with CQ, 58.5% had RII/RIII responses. No RIII failures were observed among the 112 patients who received SP, but 4.5% and 1.8%, respectively, had RII and RI responses. All 33 patients treated with MQ showed a sensitive response. Early treatment failures were observed in 27.1% of the CQ patients but in no patients receiving SP or MQ. Late treatment failures were seen in 59.3% of the CQ patients and 6.4% of the SP patients but in none of those treated with MQ. Based on these findings and because of concern about the potential for development of resistance if SP were used alone, the National Malaria Control Program is planning a change in malaria treatment policy to SP-artesunate combination therapy for this region of the country.

We assessed whether mutations in the Plasmodium falciparum multidrug-resistance gene 1 (pfmdr1) (C1034S, D1042N, and Y1246D) would predict treatment outcome during a 28-day in vivo treatment trial in the Peruvian Amazon. Mefloquine (MQ) was compared with mefloquine-artesunate (MQ-AS) in a randomized, multi-clinic protocol for the first time in the Americas. Of 115 patients enrolled in the in vivo arm, 97 patients were eligible for molecular analysis. All 97 patients remained parasite-free during 28 days of follow-up (MQ, n = 46; MQ-AS, n = 51), indicating 100% clinical efficacy of the MQ and MQ-AS treatment regimens. The reported MQ-sensitive alleles (C1034, D1042, and Y1246) were present in 48.5% (n = 47) of the cases, whereas 49 isolates (50.5%) contained the D1246 mutation reported to confer MQ resistance in vitro. However, neither this mutation nor a double mutation (S1034, D1246; n = 16) was predictive of MQ treatment outcome.

In response to the spread of chloroquine-resistant Plasmodium falciparum, Malaŵi changed its first-line antimalarial drug in 1993 from chloroquine to sulfadoxine-pyrimethamine (SP). Surveillance data has suggested that resistance to SP may be increasing. We compared the efficacy of SP with a potential successor, mefloquine (MQ). By use of a modified World Health Organization in vivo protocol, children infected with P. falciparum were randomized to receive SP (sulfadoxine 25 mg/kg) or MQ (15 mg/kg). We observed combined RII and RIII parasitologic failures of 20.0 and 22.0% in the SP and MQ arms, respectively. Among those in the MQ arm, the relative hazard of failing with a Day 2 drug level < 500 ng/mL was 10.6 times higher than those with levels > or = 500 ng/mL. Given the decreased efficacy of the first-line antimalarial drug and the high failure rates of MQ at this lower dosage, Malaŵi should consider assessing the efficacy and feasibility of alternative drugs to treat uncomplicated falciparum malaria.

Although chloroquine (CQ) resistance was first reported in Colombia in 1961 and sulfadoxine-pyrimethamine (SP) resistance in 1981, the frequency of treatment failures to these drugs in Colombia is unclear. A modified World Health Organization 14-day in vivo drug efficacy test for uncomplicated Plasmodium falciparum malaria in areas with intense malaria transmission was adapted to reflect the clinical and epidemiologic features of a low-intensity malaria transmission area in the Pacific Coast Region of Colombia. Patients > or =1 year of age with a parasite density > or =1,000 asexual parasites per microliter were enrolled in this study. Forty-four percent (24 of 54) of the CQ-treated patients were therapeutic failures, including 7 early treatment failures (ETFs) and 17 late treatment failures (LTFs). Four (6%) of 67 SP-treated patients were therapeutic failures (2 ETFs and 2 LTFs). Therapeutic failure in the CQ-treated group was associated with an age <15 years old (P < 0.01), but was not associated with initial parasite density, the presence of CQ or sulfa-containing drugs in urine, or a history of malaria. The high level of therapeutic failures to CQ detected in this study underscores the need and importance of drug efficacy evaluation in the development of a rational national antimalarial drug policy. The relatively low level of therapeutic failures to SP compared with other South American countries raises further questions regarding factors that might have prevented the rapid development of in vivo resistance to this drug combination.

Problem/condition: Malaria is caused by four species of Plasmodium (i.e., P. falciparum, P. vivax, P. ovale, or P. malariae), which are transmitted by the bite of an infective female Anopheles sp. mosquito. Most malaria infections in the United States occur among persons who have traveled to areas with ongoing transmission. Occasionally, cases occur in the United States through exposure to infected blood products, by congenital transmission, or by local mosquito-borne transmission. Malaria surveillance is conducted to identify episodes of local transmission and to guide prevention recommendations for travelers., Reporting Period: Cases with onset of illness during 1995., Description of System: Malaria cases confirmed by blood smears are reported to local and/or state health departments by health-care providers and/or laboratory staff. Case investigations are conducted by local and/or state health departments, and reports are transmitted to CDC through the National Malaria Surveillance System (NMSS). Data from NMSS serve as the basis for this report., Results: CDC received reports of 1,167 cases of malaria with onset of symptoms during 1995 among persons in the United States or one of its territories. This number represents an increase of 15% from the 1,014 cases reported for 1994. P. vivax, P. falciparum, P. malariae, and P. ovale were identified in 48.2%, 38.6%, 3.9%, and 2.2% of cases, respectively. More than one species was present in three patients (0.3% of total). The infecting species was not determined in 80 (6.9%) cases. The number of reported malaria cases acquired in Africa (n=519) remained approximately the same as in 1994 (n=517); cases acquired in Asia increased by 32.4% (n=335); and cases acquired in the Americas increased by 37.4 % (n=246). Of 591 U.S. civilians who acquired malaria abroad, 15.6% had followed a chemoprophylactic drug regimen recommended by CDC for the area where they had traveled. Nine patients became infected in the United States. Of these nine cases, five were congenitally acquired; one was acquired by organ transplantation; and one was acquired by a blood transfusion. For two of the nine cases, the source of infection was unknown. Six deaths were attributed to malaria., Interpretation: The 15% increase in malaria cases in 1995 compared with 1994 resulted primarily from increases in cases acquired in Asia and the Americas, most notably a 100% increase in the number of cases reported from South America. This change could have resulted from local changes in disease transmission, travel patterns, reporting errors, or a decreased use of effective antimalarial chemoprophylaxis. In most reported cases, U.S. civilians who acquired infection abroad were not on an appropriate chemoprophylaxis regimen for the country where they acquired malaria., Actions Taken: Additional information was obtained concerning the six fatal cases and the nine infections acquired in the United States. Malaria prevention guidelines were updated and distributed to health-care providers. Persons traveling to a malarious area should take the recommended chemoprophylaxis regimen and use personal protection measures to prevent mosquito bites. Any person who has been to a malarious area and who subsequently develops a fever or influenza-like symptoms should seek medical care; investigation should include a blood smear for malaria. Malaria infections can be fatal if not diagnosed and treated promptly. Recommendations concerning prevention and treatment of malaria can be obtained from CDC.

In October 1995 the Ministry of Public Health and Population in Haiti surveyed 42 health facilities for the prevalence and distribution of malaria infection. They examined 1,803 peripheral blood smears from patients with suspected malaria; the overall slide positivity rate was 4.0% (range, 0.0% to 14.3%). The rate was lowest among 1- to 4-year-old children (1.6%) and highest among persons aged 15 and older (5.5%). Clinical and microscopic diagnoses of malaria were unreliable; the overall sensitivity of microscopic diagnosis was 83.6%, specificity was 88.6%, and the predictive value of a positive slide was 22.2%. Microscopic diagnoses need to be improved, and adequate surveillance must be reestablished to identify areas where transmission is most intense. The generally low level of malaria is encouraging and suggests that intensified control efforts targeted to the areas of highest prevalence could further diminish the effect of malaria in Haiti.

Problem/condition: Malaria is caused by infection with one of four species of Plasmodium (i.e., P. falciparum, P. vivax, P. ovale, and P. malariae ), which are transmitted by the bite of an infective female Anopheles sp. mosquito. Most malarial infections in the United States occur in persons who have traveled to areas (i.e., other countries) in which disease transmission is ongoing. However, cases are transmitted occasionally through exposure to infected blood products, by congenital transmission, or by local mosquitoborne transmission. Malaria surveillance is conducted to identify episodes of local transmission and to adapt prevention recommendations., Reporting Period Covered: Cases with onset of symptoms during 1994., Description of System: Malaria cases confirmed by blood smear are reported to local and/or state health departments by health-care providers and/or laboratories. Case investigations are conducted by local and/or state health departments, and the reports are transmitted to CDC through the National Malaria Surveillance System (NMSS), which was the source of data for this report. Numbers of cases reported through NMSS may differ from those reported through other passive surveillance systems because of differences in the collection and transmission of data., Results: CDC received reports of 1,014 cases of malaria with onset of symptoms during 1994 among persons in the United States or one of its territories. This number represented a 20% decrease from the 1,275 cases reported for 1993. P. vivax, P. falciparum, P. malariae, and P. ovale accounted for 44%, 44%, 4%, and 3% of cases, respectively. More than one species was present in five persons (<1% of the total number of patients). The infecting species was not determined in 50 (5%) cases. The number of reported malaria cases in U.S. military personnel decreased by 86% (i.e., from 278 cases in 1993 to 38 cases in 1994). Of the U.S. civilians who acquired malaria during travel to foreign countries, 18% had followed a chemoprophylactic drug regimen recommended by CDC for the area to which they had traveled. Five persons became infected while in the United States; the infection was transmitted to two of these persons through transfusion of infected blood products. The remaining three cases, which occurred in Houston, Texas, were probably locally acquired mosquitoborne infections. Four deaths were attributed to malaria., Interpretation: The 20% decrease in the number of malaria cases from 1993 to 1994 resulted primarily from an 86% decrease in cases among U.S. military personnel after withdrawal from Somalia. Because most malaria cases acquired in Somalia during 1993 resulted from infection with P. vivax, there was a proportionately greater decrease during 1994 in the number of cases caused by P. vivax relative to those caused by P. falciparum., Actions Taken: Additional information was obtained concerning the four fatal cases and the five cases acquired in the United States. Malaria prevention guidelines were updated and distributed to health-care providers. Persons traveling to a geographic area in which malaria is endemic should take the recommended chemoprophylactic regimen and should use protective measures to prevent mosquito bites. Persons who have a fever or influenza-like illness after returning from a malarious area should seek medical care; medical evaluation should include a blood smear examination for malaria. Malarial infections can be fatal if not promptly diagnosed and treated. Recommendations concerning prevention and treatment of malaria can be obtained from CDC.

Objective: To determine the effect of transfusion on hematologic recovery and mortality among severely anemic children during and after hospitalization in rural Kenya., Design: Prospective cohort., Methods: We collected clinical and laboratory information on all severely anemic children (hemoglobin < 5.0 g/dl) and a 33% sample of children with hemoglobin < or = 5.0 g/dl who were admitted to the pediatric ward of a rural Kenyan hospital during a 6 month study period. Children were followed during hospitalization and at 4 and 8 weeks after admission., Results: Overall, 303 (25%) of the 1223 hospitalized children had hemoglobin < 5.0 g/dl, 30% of whom died during the study period. Severely anemic children who were transfused had a higher mean hemoglobin level at discharge (9.0 g/dl) than non-transfused children (5.8 g/dl, P < 0.001) and maintained a higher mean hemoglobin during the 8-week follow-up period. However, the presence of malaria parasitemia on follow-up negated the benefit of transfusion on hematologic recovery at both 4- and 8-week visits (longitudinal linear model, least square means, P > 0.05). Transfusion was associated with improved survival among children with respiratory distress who received transfusions within the first 2 days of hospitalization., Conclusions: The use of transfusion can be improved by targeting use of blood to severely anemic children with cardiorespiratory compromise, improving immediate availability of blood, and treating severely anemic children with effective antimalarial therapy.

The presently used therapy for Babesia microti infections, a combination of quinine and clindamycin, does not always result in parasitologic cures. To identify possible alternative chemotherapeutic agents for such infections, we screened, in the hamster-B. microti system, 12 antiprotozoal drugs that have either recently been released for human use or were in experimental stages of development at the Walter Reed Army Institute of Research for the treatment of malaria and leishmaniasis. Several well-recognized antimalarial drugs, such as mefloquine, halofantrine, artesunate, and artelenic acid, exhibited little or no effect on parasitemia. Two 8-aminoquinolines, WR006026 [8-(6-diethylaminohexylamino)-6-methoxy-4-methylquinoline dihydrochloride] and WR238605 [8-[(4-amino-1-methylbutyl)amino]-2,6-dimethoxy-4-methyl-5 -(3-trifluoromethylphenoxy-7) quinoline succinate], produced clearance of patent parasitemia. Furthermore, blood from infected hamsters treated with WR238605 via an intramuscular injection failed to infect naive hamsters on subpassage, thus producing a parasitologic cure. These two compounds merit further screening in other systems and may prove useful in treating human babesiosis.

Plasmodium falciparum infection is an important cause of the high childhood mortality rates in sub-Saharan Africa. Increasingly, the contribution of P. falciparum-associated severe anemia to pediatric mortality is being recognized while the impact of chloroquine resistance on mortality has not been evaluated. To address the issues of pediatric mortality, causes of death among hospitalized children less than five years of age in western Kenya were identified using standardized clinical examinations and laboratory evaluations. Follow-up examinations were conducted to determine the child's clinical status posthospitalization. Of the 1,223 children admitted to Siaya District Hospital from March to September 1991, 293 (24%) were severely anemic (hemoglobin level < 5.0 g/dL). There were 265 (22%) deaths; 121 (10%) occurred in-hospital and 144 (13%) occurred out-of-hospital within eight weeks after admission; 32% of all deaths were associated with malaria. Treatment for malaria with chloroquine was associated with a 33% case fatality rate compared with 11% for children treated with more effective regimens (pyrimethamine/sulfa, quinine, or trimethoprim/sulfamethoxazole for five days). The risk of dying was associated with younger age (P < 0.0001) and severe anemia (relative risk [RR] = 1.52, 95% confidence interval [CI] = 1.22, 1.90), and was decreased by treatment with an effective antimalarial drug (RR = 0.33, 95% CI = 0.19, 0.65). Effective drug therapy for P. falciparum with regimens that are parasitocidal in areas with a high prevalence of severe anemia and chloroquine resistance can significantly improve the survival of children in Africa.

Village-based volunteer workers have played an important role in malaria diagnosis and treatment in many different settings for more than 35 years. Two of these programs stand out in terms of their size and longevity: the Volunteer Collaborator Network of Latin America and the Village Voluntary Malaria Collaborator Program of Thailand. The success of these programs is based on a tradition of active community participation and sustained commitment and support from the national malaria control programs. As epidemiological conditions and program priorities change, these programs will have to be sufficiently flexible to keep pace. Perhaps the greatest challenge facing these single disease, vertical programs in the future is their integration into the general health services in a manner that will preserve their best features.

As part of an effort to involve community members in malaria control activities, we studied knowledge, beliefs, and practices of residents of both the Pacific coastal plain and northeastern Guatemala related to malaria transmission and Anopheles albimanus control. Most residents recognized the role of mosquitoes in malaria transmission, but few knew how mosquitoes acquired their infections or understood the risk of having an untreated person in their midst. If this were more widely known, residents might put greater pressure on infected patients to seek timely and appropriate antimalarial treatment. Seventy-three percent of families owned one or more bed nets; however, even though most informants believed that bed nets help protect against malaria, the major reason for using them was to prevent nuisance mosquito bites. It is concluded that efforts should be made to promote bed net use by seeking ways to make them more affordable and by emphasizing their effectiveness as a barrier to nuisance mosquitoes. Although residents have a very positive opinion of the National Malaria Service spray teams, it is proposed that cooperation might be improved if malaria workers would emphasize the fact that house spraying reduces the numbers of nuisance mosquitoes and other pest insects, rather than focusing solely on malaria prevention, which most informants believed was less important. This study emphasizes the importance of understanding community beliefs and practices when planning or evaluating vector control activities.

Since the late 1950s, most malaria surveillance and treatment in rural areas of Latin America has been carried out by networks of unpaid community malaria workers, known as Volunteer Collaborators, who are selected and supervised by staff of the national malaria services (NMSs) in each country. In spite of the free and readily accessible antimalarial treatment available at these Volunteer Collaborator posts, many residents continue to seek treatment elsewhere and in most cases take doses of antimalarials that are insufficient to cure their infections. To identify ways in which the Volunteer Collaborator Network could be made more attractive to residents and to improve the process of selection of new workers, we asked community residents and Guatemalan NMS workers to rank order, according to their importance, 11 qualities or characteristics of an 'ideal' volunteer malaria worker. Community residents preferred someone who is available to take care of patients at all times of the day, is a responsible person, and has a general knowledge of medicine. No significant differences were noted in the rank orders of male and female residents or literate and illiterate residents. National Malaria Service workers also preferred someone who takes care of patients at all times of the day, even when busy. In addition, they wanted individuals who recognize the importance of their work as a Volunteer Collaborator, but choosing volunteers who had a general knowledge of medicine was not important. By modifying the procedures used to select Volunteer Collaborators so as to identify candidates with the qualities preferred by residents, it should be possible to increase acceptance and improve the performance of these volunteer workers.

In most rural areas of Latin America, malaria surveillance and treatment is carried out by a network of unpaid village malaria workers, known as Volunteer Collaborators, who are trained and supervised by the National Malaria Service. To identify ways in which the performance of these volunteer workers could be improved and to test changes that would make the Volunteer Collaborator Networks (VCNs) a more attractive model for community participation in malaria case detection and treatment in other regions, we tested a series of modifications in the VCN of Guatemala. These modifications included improved methods for selecting, supervising, and evaluating the volunteer workers and for collecting blood smears and reporting results, and the use of volunteer workers, known as Volunteer Medicators, who administered presumptive antimalarial therapy without taking a blood smear. A cost-effectiveness analysis of the modified VCN was also carried out. Two years after the modifications were introduced, Volunteer Collaborators identified nearly twice as high a percentage (33% versus 17%) of patients with suspected malaria in their villages. Delays in examining blood smears were reduced from 23 days to 11 days and delays from blood smear examination to curative treatment were reduced from 21 days to 7 days. The Volunteer Medicators identified and treated only a slightly higher percentage of patients than the Volunteer Collaborators (36% versus 33%). However, the cost of maintaining a network of Volunteer Medicators ($0.61 per patient treated) was much lower than the traditional VCN ($2.45) or the modified VCN ($1.85). Thus, with a few, simple and relatively inexpensive modifications, the efficiency and cost-effectiveness of Volunteer Collaborators can be markedly improved. Additionally, the VCN can be modified to make it a more suitable model for community-based malaria control and surveillance networks in other malarious areas of the world, which differ in terms of their level of endemicity, the goals of the malaria program, or the available health care infrastructure.

The effectiveness of village-wide use of permethrin-impregnated bed nets or eave, window, and door curtains as control measures for Plasmodium falciparum malaria was evaluated during two successive high-transmission seasons in western Kenya. Pairs of villages were assigned to one of three study groups: bed net, curtain, or control. Clinical, parasitologic, and entomologic measures were made from March to July 1990 and again 12 months later. When compared with the controls in 1990 and 1991, we observed a marked reduction in the incidence of P. falciparum infections in children less than six years old in the bed net villages (reduced by 40% and 48%) and a smaller but still significant reduction in the curtain villages (10% and 33%). Significant reductions were also seen in the incidence of P. falciparum parasitemias greater than 2,500/mm3 in the bed net group (reduced by 44% and 49%) and curtain group (16% and 32%). Additionally, we observed significant reductions in the incidence of documented fevers in association with P. falciparum parasitemia in bed net (reduced by 63%) and curtain villages (53%) when compared with controls. Entomologic inoculation rates in both bed net and control villages decreased by more than 50% below control values during both high transmission seasons. The results of this study, together with a 1988 study in the same area during the low transmission season, show that bed nets offer greater year-round of protection against P. falciparum infection than curtains. However, during the high transmission season, this technique reduces the frequency of P. falciparum infection rather than preventing it entirely.

Objectives: To identify ways to improve the operation of blood-screening programs and to decrease the inappropriate use of blood by evaluating blood-transfusion practices and blood-banking services in a Kenyan hospital., Design: Prospective cohort., Setting: The study was conducted in a rural district hospital in western Kenya between September 1990 and July 1991., Methods: We collected data on all transfusion requests (blood donation, grouping, HIV screening) and blood recipients (age, sex, diagnosis, and for a 3-month period on the pediatric, maternity, and female wards, admission hemoglobin and outcome)., Results: During the 11-month study period, 799 patients received 927 transfusions: 67% were children < 15 years of age, 27% were adult women and 6% were adult men. Transfusions were often delayed due to reliance on patient-recruited donors. Patients who received blood donated on or after the date of request waited longer for transfusion (median, 3 days) than patients who received blood that had been banked and screened before the request (median, 1 day). Patient-recruited donors had a higher HIV-seropositivity rate than volunteer donors (13.4 and 4.6%, respectively; chi 2 test, P < 0.001). Overall, 47% of pediatric transfusions were classified as inappropriate: 23% did not meet the criteria of having hemoglobin < 5.0 g/dl and clinical evidence of respiratory distress, and 27% were transfused 2 or more days after requested. Among adults, 68% received one unit of blood or less., Conclusions: Improved laboratory services, reduction of unnecessary transfusions, and increased recruitment of volunteer donors are critical for improving the appropriate and timely use of blood and reducing transfusion-associated HIV transmission.

Synthetic peptides and human serum or plasma samples from regions of Brazil, Papua New Guinea, and Kenya in which malaria is endemic were used to identify B-cell epitopes localized outside the repeat region of the circumsporozoite (CS) protein of the human malaria parasite Plasmodium falciparum. In agreement with recent observations, our results confirm the presence of two non-repeat-region-based B-cell epitopes of the CS protein. Of these two epitopes, only the region I epitope (KPKHKKLKQPGDGNP) was previously shown to be recognized by human sera. In this study, we show that human immune sera from malarious regions recognize another B-cell epitope, ENANANNAV, that resides carboxyl to the repeat region. The present study reveals that (i) the repeat-sequence (NANP)-based B-cell epitope of the CS protein is an immunogenic but not immunodominant epitope; (ii) the natural expression of antibody responses to the two non-repeat-region-based B-cell epitopes of the CS protein varies in different populations in which malaria is endemic; (iii) although the host immune responses to the non-repeat-region-based B-cell epitopes increase as a function of host age, this increase is not statistically significant for the region I epitope but is significant for the other epitope; and (iv) the Th1R T-cell site but not the Th2R or Th3R T-cell site induces an antibody response in the human host. This study confirms the immunogenic potential of non-repeat-region-based B-cell epitopes and suggests that antibody pressures may also contribute to the maintenance of the antigenic diversity of the CS protein.

In Africa, blood transfusions are frequently given to treat severe paediatric anaemia. Because of the risk of HIV transmission, identification of when transfusion will reduce the risk of death for severely anaemic children has become increasingly important. For all children admitted to a Kenyan hospital from October, 1989, to October, 1990, we collected data on clinical presentation, haemoglobin (Hb), receipt of transfusion, and in-hospital survival. Of 2433 admissions, 29% (684) had severe anaemia (Hb less than 5.0 g/dl), and 20% (483) received blood transfusions. Based on laboratory criteria only, children with Hb less than 3.9 g/dl who were transfused had lower mortality than those with Hb less than 3.9 g/dl who were not transfused, but this finding applied only to children transfused on the day of admission (odds ratio [OR] 0.30; 95% Cl 0.14, 0.61) or the day after admission (OR 0.37; 95% Cl 0.14, 1.00). Based on a combination of laboratory and clinical criteria, children with clinical signs of respiratory distress and Hb less than 4.7 g/dl who were transfused had lower morality than those who were not (OR 0.19; 95% Cl 0.09, 0.41). Among children without respiratory distress, there was no association between receipt of transfusion and mortality, irrespective of admission Hb. The frequency of blood transfusion can be reduced and survival enhanced by targeting blood to those children with severe anaemia and clinical signs of respiratory distress, and by using transfusion early in the course of hospitalisation.

We tested the ability of a recombinant DNA-encoded fragment (C7Ag) of a Plasmodium falciparum merozoite protein (p75) and of two carrier-free peptide models (28-mer and 76-mer) to stimulate boostable antibody responses in Aotus nancymai monkeys. In addition, we evaluated protection against challenge with the Uganda Palo Alto (FUP) strain of this parasite. The data indicate that C7Ag elicited a strong and boostable IgG antibody response in all the monkeys immunized. However, studies with the peptide models demonstrated that various animals produce antibodies to different portions of this structure. When the post-boost sera from monkeys immunized with C7Ag were analyzed for reactivity against two major portions of C7Ag, most of the antibody response was observed against the disulfide-bonded 76-residue region that forms a conformational immunogenic epitope. In the same sera, antibody levels against the charged helical region modeled with a 28-mer were generally low. Immunization with synthetic peptides revealed that the 76-mer stimulated an antibody response almost as strong as C7Ag, with substantial cross-reactivity against the parasite antigen. The 28-mer evoked a response that was not efficient or uniform, and showed little reactivity with the authentic parasite antigen. Aotus nancymai was shown to be susceptible to infection with the Uganda Palo Alto strain of P. falciparum; however, maximum parasitemia varied markedly in both immunized and control monkeys. Statistical analysis failed to recognize differences in maximum parasitemia between the vaccine and control groups. The variation in maximum parasitemia suggests that the FUP strain in this species of Aotus is a poor model for the detection of differences in efficacy based on maximum parasitemia. This initial study with structures based on parts of the 75-kD merozoite surface antigen of P. falciparum indicated that both the recombinant-produced protein C7 and the 76-mer synthetic peptide, when combined with a Syntex adjuvant formulation, were safe and immunogenic in A. nancymai monkeys. However, the data emphasize the problems of using animal models to evaluate the potential effects of immunogens in humans.

Surveys of residents of the Pacific coast of Guatemala revealed a lack of knowledge and many misconceptions about the transmission and treatment of malaria, which could adversely affect malaria control measures and antimalarial therapy. Although mosquitoes are known to play an important role in malaria transmission and are thought to become infected by biting individuals with malaria, 75% of people interviewed believe that the mosquitoes can also acquire infections from contaminated water or by biting snakes and frogs. Furthermore, most residents believe that malaria can be acquired in other ways, such as by bathing too frequently or by drinking unboiled water. Although self-treatment of malaria with oral and injectable drugs purchased at stores and pharmacies is very common, less than 10% of the respondents were aware of the correct curative dose of chloroquine. Chloroquine injections are preferred to tablets and believed to be approximately three times as potent as tablets of the same concentration. Nearly two-thirds of the interviewees believed that pregnant and lactating women with malaria should avoid the use of chloroquine because it may cause a spontaneous abortion or dry up breast milk. Similar surveys of National Malaria Service workers and village malaria workers revealed higher levels of knowledge, although the village workers had many misconceptions about malaria transmission. An educational campaign directed at correcting some of these misconceptions should result in more appropriate self-treatment of malaria and greater acceptance by residents of personal protection methods and vector control and drug treatment programs.

To evaluate the effectiveness of the Volunteer Collaborator Network (VCN) of Latin America as a community-based malaria case detection and treatment system, we conducted a study of the VCN of Guatemala. Volunteer Collaborators took 72.6% of all blood smears and identified 81.3% of all malaria cases reported by the Guatemalan National Malaria Service. The average volunteer treated 5.8 patients per month (range 0-32.8). In contrast, passive case detection (PCD) posts in government hospitals and health centers treated an average of 12.5 patients per month (range 0.5-91.4). The slide positivity rate of blood smears taken by Volunteer Collaborators was 16.2% compared with 9.7% for PCD posts in health centers and 10.3% for malaria workers during active case detection. The average delay between the date a blood smear was taken and examined ranged from 18.1 days on the Pacific coastal plain to 26.3 days in the less accessible northern region of the country. An additional 14.5 to 47.6 days elapsed before the radical treatments were initiated in these two regions. Seventy percent of the patients completed their radical treatments. In a survey conducted on the Pacific coastal plain of Guatemala, of 1,021 patients with chills and/or fever who believed they had malaria, 20.0% had visited a Volunteer Collaborator and 4.9% were treated at a government health center. Thus, the PCD network detected only 25% of all patients with symptoms suggestive of malaria. Most of the remaining patients treated themselves with antimalarial medications purchased in stores and pharmacies, but less than 15% of these patients used adequate courses of therapy. Furthermore, the rate of detection of symptomatic patients with malaria varied considerably from one community to another. Thus, data from the VCN are probably most useful when groups of communities or geographic areas are stratified for malaria control activities because at this level, variations between individual Volunteer Collaborator posts will be minimized. In spite of these problems, the VCN remains an excellent source of epidemiologic data for malaria control programs and the most practical means available for providing timely, appropriate antimalarial therapy to febrile patients in rural areas.

The Volunteer Collaborator Networks (VCNs) of Latin America are one of the oldest and most successful examples of community participation in malaria control. They are made up of unpaid community volunteers, known as Volunteer Collaborators, who are selected by their neighbors and are trained and supervised by a member of the National Malaria Service (NMS). When a febrile patient visits the home of a Volunteer Collaborator, the volunteer worker takes a thick blood smear, completes a patient report form, and administers a presumptive treatment for malaria. The blood smear is examined in an NMS laboratory, and if malaria parasites are found, a radical or curative treatment is forwarded to the Volunteer Collaborator so that it can be administered to the patient. There is no charge for either the blood smear or the antimalarial medication. The VCN of Guatemala was established in 1958. Currently, more than 5,000 Volunteer Collaborator posts are operating throughout the malarious areas of the country. The volunteers range in age from 12 to 76 years old and 61% are men. Approximately 15% have no formal education, and only 27% have a sixth grade or higher education. The median length of service is 35 months (range three months to 26 years); 33% have worked for five or more years. Male Volunteer Collaborators had significantly lower turnover rates than females, as did married Volunteer Collaborators when compared with single volunteers. An inverse relationship was noted between the amount of education a Volunteer Collaborator had and his length of service. With modifications tailored to meet the objectives of a malaria control program and the local epidemiologic setting, the VCN can serve as an excellent model for community participation in malaria case detection and treatment in other regions of the world. In particular, in areas where the primary goal of the malaria program is to prevent mortality and morbidity through the provision of readily accessible, appropriate drug therapy, VCNs are an attractive alternative to self-medication and an effective adjunct to treatment of malaria at health posts which are often located at a considerable distance from the patient's village. Experience gained with this system can be valuable in developing approaches to community involvement in other efforts to improve the health of villagers in developing countries.

The role of circulating peripheral blood momonuclear cells (PBMC) in mediating protective immunity was examined during an immunization trial in Saimiri monkeys. Three engineered constructs representing different but overlapping regions of the circumsporozoite (CS) protein of Plasmodium vivax were used to immunize the Saimiri monkeys. Monkeys were randomly placed into three immunization groups: rPvCS2, rPvCS3, and LCV3 (representing three different but overlapping portions of the P. vivax CS protein) and two control groups: an alum adjuvant control group and an unimmunized control group. Collections of PBMC were made throughout the study at weeks 0, 2, 8, challenge (week 16), and two weeks after challenge. Proliferative responses to all immunogens and pokeweed mitogen were measured in all monkeys. Fourteen of 18 monkeys immunized with either rPvCS2 or rPvCS3 responded on the day of challenge to the appropriate immunogen with a stimulation index less than 2. Immunization with LCV3, which represents the repeat region only, elicited a specific response in only one monkey. However monkeys in both control groups also responded to rPvCS2 and rPvCS3, regardless of immunization, suggesting the presence of epitopes in rPvCS2 and rPvCS3 capable of associating with differing MHC antigens. Furthermore, the frequency of these cells in the periphery was increased by immunization, as demonstrated by a greater number of responding monkeys in the rPvCS2 and rPvCS3 immunized groups.

Aotus nancymai were immunized with the 4-mer, 8-mer, and 11-mer repeat peptides of the ring-infected erythrocyte surface antigen molecule of Plasmodium falciparum conjugated to diphtheria toxoid with muramyl dipeptide (MDP) as adjuvant. Immunization failed to induce protective immunity against the Uganda Palo Alto strain of P. falciparum as judged by maximum levels of parasitemia of immunized monkeys relative to those of controls. The fused polypeptide FPAg632, when combined with MDP, also failed to induce protective immunity. However, the maximum level of parasitemia and serologic response to the 11-mer peptide were inversely correlated. The safety of the use of MDP was evident.

Reported are the results of a trial in squirrel monkeys of 2 Plasmodium vivax malaria vaccine candidates based on the circumsporozoite (CS) protein, namely, rPvCs-2 and rPvCS-3. Compared with an earlier recombinant P. vivax CS construct, rPvCS-1, rPvCS-2 has an additional 24 amino acids at the C-terminal, which includes the thrombospondin region of homology and a putative T cell epitope. The rPvCS-3 was generated from a chemically synthesized gene that contained an additional 54 amino acids at the amino terminus and terminates at the same carboxy-terminal amino acid as rPvCS-2. In addition, rPvCS-3 contained only 1 each of the repeat sequences DRADGQPAG and DRAAGQPAG. Both antigens were administered with alum as adjuvant. Neither formulation caused toxic side effects and both recombinant molecules induced high antibody titers. Two monkeys were protected against sporozoite challenge by immunization with rPvCS-2 antigen, while none of the rPvCS-3 immunized animals displayed any degree of protection. While there was no correlation between protection and antibody titer or the in vitro proliferation of lymphocytes in response to the antigens, this is further evidence to support the role of the repeating epitopes in generating protective immunity.

A strain of Plasmodium brasilianum was isolated from a naturally infected Saimiri monkey from Peru and subsequently passaged to 21 splenectomized Saimiri sciureus boliviensis monkeys. Nine of 12 attempts to transmit infection by sporozoite inoculation were successful with prepatent periods ranging from 23 to 41 days. Gametocytes were infective to Anopheles freeborni, Anopheles stephensi, Anopheles dirus, Anopheles maculatus, and Anopheles gambiae mosquitoes. The strain demonstrated a high level of resistance to cure with chloroquine.

The effectiveness of permethrin-impregnated (0.5 g/m2) bed-nets and curtains as malaria control measures was evaluated in Uriri, Kenya in 1988. One hundred five families were randomly assigned to 1 of 3 study groups (control, bed-net, or curtain). All participants were cured of parasitemia with pyrimethamine/sulfadoxine. Selective epidemiologic and entomologic parameters were measured weekly, while knowledge, attitude, and practices surveys were conducted at the beginning and end of the 15 week study. Plasmodium falciparum infections per person week at risk were significantly higher in the control group than in either the curtain group (5.42 vs. 2.35 cases/100 person weeks risk) or the bed-net group (5.42 vs. 3.77 cases/100 person weeks risk). The curtain group had fewer infections per person week at risk than the bed-net group (2.35 vs. 3.77 cases/100 person weeks risk). A difference was found in clinical malaria among the groups: 45% of persons in the bed-net and curtain groups vs. 30% of those in the control group reported no episodes of fever and chills (chi 2, P less than 0.05). Indoor resting Anopheles gambiae or An. funestus were found on 94 occasions in the control houses, but only twice in the treated houses during weekly visits to each house over the study period (chi 2 P less than 0.001). The pyrethrum knockdown method produced similar results with a total of 195, 23, and 3 An. gambiae and An. funestus collected in the control, bed-net, and curtain houses during the same period, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

We evaluated the use of illiterate community volunteers for malaria case detection and treatment in Guatemala. Volunteer workers, known as Volunteer Medicators, were selected by members of their communities and were trained and supervised by National Malaria Service (NMS) staff. Their responsibilities included recording basic demographic data and administering a three-day course of chloroquine (25 mg kg-1) to all febrile patients who visited their homes. Patient information was recorded on a special form which consisted of stick-figure drawings. During a one-year evaluation period, no differences were noted between literate and illiterate Volunteer Medicators with respect to the length of time required for their training or supervision, the average number of patients they treated per month, the frequency of errors in recording data or administering medication, or their acceptance by the community residents.

Between Jan 1 and Oct 31, 1975, a cluster of ten cases of pneumocystis pneumonia occurred in children with acute lymphocytic leukemia (ALL) at the James Whitcomb Riley Hospital for Children in Indianapolis. The risk of infection appeared to be related to the intensity of chemotherapy. Furthermore, illness developed in nine of the ten patients between 30 and 100 days after initiation of therapy, suggesting a period of heightened susceptibility to infection. An indirect immunofluorescent test was used to detect antipneumocystis antibodies in serum samples collected from patients with pneumocystis pneumonia and their contacts. Members of the Riley Hospital staff who had close contact with infected children had a higher prevalence of elevated antibody titers (7/12) than other staff members (2/22; P = .004) or parents of infected patients (0/8; P = .01). This suggests that transmission of pneumocystis may occur within the hospital environment.

The eradication of malaria remains an elusive goal in many tropical and subtropical countries, even though methods are available that, if used correctly, will permit control of the disease in most area. These methods include chemotherapy directed against the parasite in the human host and such antivector techniques as a reduction of mosquito breeding sites and an attack on the aquatic and adult stages of mosquitoes. The direction of a malaria control program requires a detailed understanding of malaria epidemiology and control measures as well as flexibility in their application to different epidemiologic situations. In most developing countries, the success of a malaria control effort will depend on a well-functioning primary health care system and active community participation in control activities.

We report a trial in squirrel monkeys of 2 recombinant Plasmodium vivax malaria vaccine candidates based on the circumsporozoite (CS) protein. One recombinant (NSl81V20), produced in Escherichia coli, contains the repeat region of the CS protein. The other (VIVAX-1) recombinant is yeast-derived and contains the entire repeat domain and part of the surrounding N-terminal and C-terminal regions. Both antigens were administered with alum and muramyl tripeptide as adjuvants. No formulations caused toxic side effects. Both antigens, when administered with alum, induced high levels of sporozoite antibodies in all animals. Another group of animals was immunized with irradiated sporozoites alone. Upon challenge, a few immunized animals did not develop detectable parasitemia and others developed parasitemia only after a prolonged prepatent period. Monkeys immunized with irradiated sporozoites had higher levels of antibody but no increased protection. There was no correlation between protection and either antibody level or the in vitro proliferation of lymphocytes in response to the antigens. This is the first time P. vivax sporozoite vaccines have been tested in monkeys with a subsequent sporozoite challenge.

Blood smears from 13 patients infected with Babesia microti were reviewed to define the range of morphologic characteristics of the organism. Organisms resembling rings of Plasmodium falciparum were the predominant forms in all patients' blood smears. Babesia microti and Plasmodium spp. may be differentiated by the presence of pigment deposits in erythrocytes parasitized with mature stages of Plasmodium.

An indirect immunofluorescent test was used to determine antibody titers to Babesia microti in serum samples collected from 16 patients between 1 week and 1 year after the onset of illness. Titers rose to greater than or equal to 1:1,024 during the first few weeks of illness and then fell gradually to 1:16 to 1:256 over the next 5-6 months.