Vector studies and epidemiology of malaria in Irian Jaya, Indonesia

Human populations in the low-land littoal of southwestern Irian Jaya are exposed to holoendemic malaria, principally caused by P. falciparum. The spleen rate in children of ages 2-9 years, in 4 villages ranged from 78% to 97%, and parasite prevalences were from 21% to 52%. Three known vectors of malaria, An. farauti, An. koliensis and An. punctulatus, were present, the latter two being most abundant. One specimen of each of the latter two species, upon dissection, was found carrying sporozoites in thoracic tissue. Larval habitats were numerous in peridomestic sites, including drainage ditches, natural ground pools and plots of Ipomea reptans; thus the vector populations were always in close contact with the human populations.

Prelminary examination of rabbit conjunctival mucins

Conjunctival mucins from albino rabbits were fractionated using gel filtration and anion-exchange chromatography. Charge homogeneity of the various conjunctival mucin fractions was confirmed by polyacrylamide gel electrophoresis. The molecular weight characteristics of the isolated fractions varied with the analytical scheme employed. Two schemes yielded mucins with molecular weights of 10(4), 10(5), and 10(6). However, when anion-exchange chromatography was the first step in the fractionation scheme, the dominant mucin had a molecular weight of 1.7 x 10(5). In contrast, when gel filtration chromatography was the first step, the dominant mucin had a molecular weight of 5.7 x 10(4). It was postulated that during migration through the anion-exchange matrix, the low molecular weight conjunctival mucin underwent trimer formation. Comparison with the mucin fractions isolated from tear mucoid threads revealed that the scheme beginning with anion-exchange chromatography preserved the fractionation pattern seen in tear mucoid threads. This result implies that conjunctival mucins undergo an association prior to or after their entry into the tear film. The molecular event of interest in this process is self-association of the species with a molecular weight of 5.7 x 10(4), resulting in a trimer with a molecular weight of 1.7 x 10(5). This trimer appears to resist deaggregation on exposure to a medium of lesser ionic strength. Several explanations are offered for its formation as well as for its stability. The implication of multiple conjunctival (tear) mucins for tear film stability also is discussed.

Corneal metabolism of pilocarpine in pigmented rabbits

Cornea, aqueous humor, and iris-ciliary body levels of pilocarpine and its metabolite pilocarpic acid were determined in mixed-breed rabbits following topical dosing with 25 microliters of 1 X 10(-2) M pilocarpine. From the time-drug concentration profile it is clear that extensive metabolism of pilocarpine occurs in the cornea of pigmented rabbits. This finding contrasts sharply with similar studies in albino rabbits where relatively low levels of pilocarpine acid were observed. It is estimated that the first-order metabolism rate constant in albino rabbits is approximately two orders of magnitude smaller than in pigmented animals. A significant observation from this finding is the possibility that the reported greater dose requirement for heavily pigmented individuals may not be due to drug-pigment binding alone but also to extensive corneal drug metabolism.

Mechanistic and quantitative evaluation of precorneal pilocarpine disposition in albino rabbits

The low ocular bioavailability of topically applied pilocarpine is attributed to extensive precorneal drug loss in conjection with the resistance to corneal penetration. Several elements of precorneal loss were reported earlier, but a complete mechanistic understanding has not been available. The present study was designed to gain a better understanding of the mechanisms governing pilocarpine disposition in the precorneal areas as well as the relative influence of these parameters on ocular drug bioavailability. Radioactive pilocarpine and glycerin solutions were instilled into the precorneal area of the albino rabbit eye under various experimental conditions, and the drug concentration in the lacrimal lake was monitored as a function of time. The results demonstrated that nonconjunctival loss of pilocarpine, vasodilation due to the drug, and lacrimation due to vehicle formulation are additional aspects of precorneal drug disposition. The individual influence of all precorneal loss parameters on drug bioavailability was then assessed using a mathematical model formulated from experimental findings on both precorneal and intraocular drug disposition. Drainage and vasodilation, as well as nonconjunctival pilocarpine loss, exerted major influences on drug loss at the absorption site.

Crimean-congo hemorrhagic fever, Thogoto, dugbe, and Jos viruses isolated from ixodid ticks in Ethiopia

From 1974 through 1976, U.S. Naval Medical Research Unit No. 5 isolated 25 strain of tick-borne virus in infant mice from 410 pools containing over 6,000 ticks, and one strain from a bird and one strain from a rodent collected in central and southern Ethiopia. Of these, 17 were identified as known viruses previously found in West Central and East Africa. There were 8 strains of Jos virus from Amblyomma ticks; 7 strains of Dugbe virus from a bird, a rodent and from ticks; 1 strains of Crimean-Congo hemorrhagic fever virus and 1 strain of Thogoto virus from ticks.

The 1970 yellow fever epidemic in Okwoga District, Benue Plateau State, Nigeria. I. Epidemiological observations

A focal epidemic of yellow fever occurred in late 1970 in southern Benue Plateau State, Nigeria, 1 year after a much larger outbreak in northern Nigeria. Like its predecessor, the 1970 epidemic was associated with virus transmission by wild-breeding Stegomyia mosquitos. Epidemiological data on the outbreak are reported in this paper.

The 1970 yellow fever epidemic in Okwoga District Benue Plateau State, Nigeria. 2. Immunity survey to determine geographic limits and origins of the epidemic

Serological surveys undertaken to define the geographic limits of the 1970 rural yellow fever epidemic in Okwoga District, Nigeria, indicated that surrounding areas of Benue Plateau State and East Central State were not involved. However, the surveys uncovered a separate focus of unrecognized, recent epidemic yellow fever in Mbawsi, in southern East Central State. The highest proportions of yellow-fever-immune sera outside the Okwoga and Mbawsi foci were found in zones of Guinea savannah in the Benue River basin.

Ecological aspects of the Jos Plateau, Nigeria

The Jos Plateau has an area of about 6 700 km(2), lies at 1 280 m above sea level, and contains approximately 1 million inhabitants. Annual rainfall averaged 137 cm in the period 1965-68; in 1969 rainfall totalled 170 cm and lasted for a month longer than usual.The rural population is engaged in agriculture, tin mining, and cattle grazing. Animal life consists chiefly of domestic species; there are few large wild animals. Wild primates are apparently rare, although baboons and red patas monkeys are sometimes seen. Tree cover is restricted to small patches along streams and some hillsides; there are euphorbia hedges and scattered trees in rural communities and along roadsides.