Morphological and Molecular Diagnosis of Necator americanus and Ancylostoma ceylanicum Recovered from Villagers in Northern Cambodia.

Human hookworm infections caused by adult Ancylostoma spp. and Necator americanus are one of the most important tropical diseases. We performed a survey of intestinal helminths using the Kato-Katz fecal examination technique targeting 1,156 villagers residing in 2 northern provinces (Preah Vihear and Stung Treng) of Cambodia in 2018. The results revealed a high overall egg positive rate of intestinal helminths (61.9%), and the egg positive rate of hookworms was 11.6%. Nine of the hookworm egg positive cases in Preah Vihear Province were treated with 5-10 mg/kg pyrantel pamoate followed by purging with magnesium salts, and a total of 65 adult hookworms were expelled in diarrheic stools. The adult hookworms were analyzed morphologically and molecularly to confirm the species. The morphologies of the buccal cavity and dorsal rays on the costa were observed with a light microscope, and the nucleotide sequences of mitochondrial cytochrome c oxidase subunit 1 (cox1) gene were analyzed. The majority of the hookworm adults (90.7%) were N. americanus, whereas the remaining 9.3% were Ancylostoma ceylanicum, a rare hookworm species infecting humans. The results revealed a high prevalence of hookworm infections among people in a northern part of Cambodia, suggesting the necessity of a sustained survey combined with control measures against hookworm infections.

Necator americanus: maintenance through one hundred generations in golden hamsters (Mesocricetus auratus). II. Morphological development of the adult and its comparison with humans.

Through 100 passages, the human hookworm Necator americanus was adapted to the golden hamster, Mesocricetus auratus, without either the requirement for exogenous steroids or other immunosuppressive agents, nor the requirement to infect hamsters as pups. Adult N. americanus recovered from infected hamsters were morphologically similar to those from infected humans in Sichuan Province, China, although they were smaller and the females produced fewer eggs. The natural history and kinetics of N. americanus infection was different in female and male hamsters. Female hamsters supported low intensity infections that lasted for approximately two months. In contrast, the peak intensity of infection in male hamsters was high, but this situation lasted less than for 4 weeks at which time many of the hookworms were expelled. However, even after the major parasite expulsion, the total number of hookworms consistently remained higher in chronically infected male hamsters compared with female hamsters. The hamster model of N. americanus is potentially useful for studying the development of new anthelminthic drugs and vaccines.

Long PCR-based amplification of the entire mitochondrial genome from single parasitic nematodes.

Mitochondrial genome sequences provide useful markers for investigating population genetic structures because of their maternal inheritance and high evolutionary rates. There is, however, a paucity of information on mitochondrial genomes for many parasitic organisms, including nematodes, which appears to relate mainly to technical limitations and (for modestly funded laboratories) the cost associated with full mitochondrial genome sequencing. In this article, we describe a simple, relatively inexpensive long-PCR approach for the amplification (using two sets of primers) of the entire mitochondrial genome from individual parasitic nematodes for subsequent sequencing, which overcomes these limitations. We employed two species of human hookworm (Ancylostoma duodenale and Necator americanus; order Strongylida) to establish the long-PCR conditions, and then extended its use to a number of other species of parasitic nematode of the class Secernentea (orders Strongylida, Ascaridida and Rhabditida). The long-PCR method for the amplification of the entire mitochondrial genome from single nematodes, coupled with direct sequencing of amplicons, provides a useful tool for the comparative analysis of genome organisation and evolution of a range of nematode groups. It also creates a platform for molecular ecological and population genetic studies.

[Scanning electron microscopic observations on the copulatory spicules of the male Necator americanus and Ancylostoma duodenale].

Scanning electron microscopic observations were made on the morphological structures of the two copulatory spicules of the male Necator americanus and Ancylostoma duodenale. In both species, one of the two copulatory spicules was in the shape of a concave groove and the other, in the shape of an oblate tube. Owing to the difference in the concavity of the groove shaped copulatory spicule between the two species as shown by the cross sections, Necator americanus usually appear to have only one copulatory spicule whereas Ancylostoma duodenale usually show two separate copulatory spicules in appearance (Figs 1-10).