Paralytic shellfish poisonings resulting from an algal bloom in Nicaragua

Background

During an October 2005 algal bloom (i.e., a rapid increase or accumulation in the population of algae) off the coast of Nicaragua, 45 people developed symptoms of paralytic shellfish poisoning (PSP) and one person died. PSP in humans is caused by ingestion of saxitoxin, which is a neurotoxin often associated with shellfish contaminated by algal blooms.

To explore the relationship between the algal bloom and human illnesses, we performed a case-control study of residents living in a coastal island. We administered a standardized clinical questionnaire, sampled locally harvested seafood and algae, and obtained urine samples for saxitoxin testing from symptomatic and asymptomatic persons. PSP case-patients were defined as island residents who developed at least one neurological symptom during the November 4–16 intoxication period. Seafood and algal samples were analyzed for saxitoxins using the receptor-binding assay and high-performance liquid chromatography. Two urine samples were analyzed for saxitoxins using a newly developed immunoassay.

Findings

Three shellfish and two algal samples tested positive for saxitoxins. Ten (9%) of 107 participants developed neurological symptoms during the specified time period and five required hospitalization. While 6 (67%) of 9 possible case-patients and 21 (21%) of 98 controls had eaten fish (p=0.008), all case-patients and 17 (17%) of controls had eaten clams (P<0.0001). The saxitoxin concentration in the urine of a hospitalized case-patient was 21 ng saxitoxin/g creatinine compared to 0.16 ng saxitoxin/g creatinine in the single control patient’s urine.

Conclusions

These findings suggest that a bloom of saxitoxin-producing algae resulted in saxitoxin accumulation in local clams and was responsible for the PSP intoxication.

Positive association of renal insufficiency with agriculture employment and unregulated alcohol consumption in Nicaragua

BACKGROUND AND OBJECTIVES

Endemic renal insufficiency (RI) of unknown etiology is a major public health issue with high mortality in the Pacific coastal regions of Central America. We studied RI in León and Chinandega, Nicaragua, evaluating associations with known risk factors and hypothesized exposures.

METHODS

A cross-sectional survey was conducted with assessment of medical, social, and occupational history and exposures in conjunction with measurement of serum creatinine. Cases were defined by an estimated glomerular filtration rate (eGFR) <or=60 mL/min/1.73 m(2) using the modified four-variable Modification of Diet in Renal Disease (MDRD) study equation for non-African Americans. Logistic regression models controlling for known risk factors of kidney disease were used to evaluate associations between exposures and RI.

RESULTS

A total of 124 RI cases were compared to 873 persons without RI. Cases had no significant differences in the odds of having a systolic blood pressure (SBP) > 140 or diastolic blood pressure (DBP) > 90 mmHg, or in reporting diabetes. Agricultural labor was associated with RI (OR = 2.48, 95%CI: 1.59, 3.89, p < 0.0001). There was no association with agricultural non-field work (OR = 0.91, 95%CI: 0.60, 1.38, p = 0.65). Consumption of unregulated alcohol ("lija") was associated with RI (OR = 2.10, 95%CI: 1.31, 3.39, p = 0.0023), as was drinking 5 L or more of water per day (OR = 3.59 vs. 1 L 95%CI: 1.52, 4.46, p = 0.0035).

CONCLUSIONS

Agricultural field labor and lija consumption were associated with RI in this region. Water intake may also be important. Identifying specific risk factors for RI within these exposures, such as individual pesticides or lija ingredients, may facilitate prevention in a setting where dialysis and transplantation are limited.

An epidemiologic and entomologic investigation of a cluster of Rocky Mountain spotted fever cases in Delaware

BACKGROUND

Rocky Mountain spotted fever (RMSF) continues to be the most common fatal tick-borne illness in the United States. In August of 1996, four children attending a summer camp in Delaware were diagnosed with RMSF. This report summarizes the results of the epidemiologic and entomologic investigation conducted by the Delaware Division of Public Health and the Centers for Disease Control and Prevention regarding this cluster of RMSF cases. Epidemiologic and clinical aspects of RMSF, as well as previously reported clusters of the disease, are also reviewed.

METHODS

A questionnaire regarding symptoms and activities was administered via telephone to 163 (73 percent) of the 223 attendees. A suspected case was defined as an illness in a person attending the camp between August 11 and 17 that occurred during the two-week period following the session, characterized by either 1) fever with one or more symptoms (i.e., headache, rash, myalgia, or fatigue) or 2) no fever with two or more symptoms. Cases of RMSF were confirmed by serologic evaluation.

RESULTS

Seven of 13 patients with suspected RMSF submitted sera for testing. Four patients had confirmed RMSF; three were males, and the median age was 12.5 years compared with 12 years for all attendees. All confirmed patients reported fever, headache, fatigue, and rash. An increased risk of becoming ill was associated with overnight camping at site A (Odds Ratio (OR) undefined, p = 0.02), visiting or overnight camping at site B (OR undefined, p = 0.003 and 0.002), and leaving the trails when hiking (OR undefined, p = 0.02).

CONCLUSIONS

These data suggest that development of RMSF was associated with visiting or camping at specific sites and behavior likely to increase contact with ticks. Camp supervisors were advised to educate campers regarding tick bite prevention measures, reduce underbrush around campsites, and encourage campers to remain on the trails. Health care providers should remain aware of the increased risk for RMSF during the spring, summer, and fall months.