Comparison of rates of infection by the Lyme disease spirochete in selected populations of Ixodes dammini and Amblyomma americanum (Acari: Ixodidae).

At a major endemic focus in New Jersey, 50% of 290 adult Ixodes dammini collected in the fall of 1984 were infected with the Lyme disease spirochete (Borrelia burgdorferi), which was statistically higher than the rate found in the 202 adult ticks (39.6%) examined during the spring. Neither sex nor site of collection within the focus significantly affected the infection rate. The observed infection rates were similar to those reported in endemic areas of New York and Connecticut. Borrelia burgdorferi also infected all active stages of Amblyomma americanum ticks. Rates of infection were 5.4% in adults (n = 467) and 3.4% in nymphs (n = 289); 15.6% of clusters of unengorged larvae harbored B. burgdorferi, suggesting transovarial passage of the spirochete. Comparison of the rates of infection in I. dammini and A. americanum and their potential impact on Lyme disease transmission is discussed.

Determination of cobalt and zinc in highpurity niobium, tantalum, molybdenum and tungsten metals by atomicabsorption spectrophotometry after separation by extraction.

A method for determining 0.0005-0.05% of cobalt and zinc in high-purity niobium, tantalum, molybdenum and tungsten metals by atomic-absorption spectrophotometry is described. After sample dissolution, cobalt and zinc are separated simultaneously from the matrix materials by chloroform extraction of their thiocyanatediantipyrylmethane ion-association complexes, at pH 3.25, from a citric acid medium approximately 1.2M in sodium thiocyanate. Interference from copper is eliminated with thiourea. Large amounts of iron interfere under the recommended conditions, but moderate amounts may be present in the sample solution without causing appreciable error in the results. Phosphorus (as orthophosphate) interferes in the extraction of cobalt from tungsten solutions. Moderate amounts of other impurities do not interfere in the proposed method.