Morphological identification of parasitic nematode infective larvae of small ruminants and cattle: a practical lab guide.

In 2004, a new concept was introduced for simplifying identification of larvae of the common nematodes of cattle, sheep and goats that comprises estimates of the lengths of the sheath tail extensions of infective third-stage larvae (L3) of each genus and/or species to that of Trichostrongylus spp., instead of having to be dependent only on measurements in micrometre. For example, if the mean length of the sheath tail extension (the extension of the sheath caudad, beyond the caudal tip of the larva) of Trichostrongylus colubriformis and Trichostrongylus axei is assumed to be 'X', then that of Haemonchus contortus is 2.0-2.7 'X' - a difference that is not difficult to estimate. An additional new approach suggested now, particularly for L3 of species and/or genera difficult to differentiate (such as Chabertia ovina and Oesophagostomum columbianum), is to estimate the proportion of the larval sheath tail extension comprising a terminal thin, whip-like filament. For the experienced person, it is seldom necessary to measure more than one or two sheath tail extensions of L3 in a mixed culture, because the identity of most of the remaining L3 can thereafter be estimated in relation to those measured, without having to take further measurements. The aim of this article was to present the novel approach in the form of a working guide for routine use in the laboratory. To facilitate identification, figures and a separate organogram for each of small ruminants and cattle have been added to illustrate the distinguishing features of the common L3.

Morphological variability within Oesophagostomum bifurcum among different primate species from Ghana.

Adult Oesophagostomum bifurcum (Nematoda: Strongylida) from human and non-human primates from Ghana were compared in order to investigate the extent of morphological variability within the species. Using analysis of variance and principal component analysis, significant differences in morphological characters (such as parasite length, width, length of the oesophagus and length of spicules) were demonstrated between O. bifurcum worms from humans, the Mona, Patas or Green monkey and/or Olive baboons. These findings suggest that O. bifurcum from different species of primate host represent distinct population variants, also supported by recent epidemiological and genetic studies of O. bifurcum from such hosts.

Morphological identification of nematode larvae of small ruminants and cattle simplified.

A simplified system has been developed to facilitate identification of nematode larvae of the common nematodes of cattle, sheep and goats. Firstly, in addition to the characteristics conventionally used for identification (such as the shape of the cranial extremity and numbers of intestinal cells), the lengths of the infective sheath tails of infective larvae of each genus/species are related to that of Trichostrongylus spp. instead of using measurements for differentiation. For instance, if the mean length of the sheath tail (the distance the sheath extends caudad beyond the caudal tip of the larva) of Trichostrongylus spp. is assumed to be "X", then that of Haemonchus contortus is 2-2.7"X", and that of Oesophagostomum spp. from sheep is 4-7"X", etc. Secondly, by estimating the proportion of the sheath tail of a larva comprised of a terminal thin whip-like filament, identification is aided, particularly in those L3 of species that resemble one another closely, such as Chabertia ovina and Oesophagostomum venulosum or Oesophagostomum columbianum. After some practice with the system it is usually necessary to measure only one or two sheath tails of L3 in a mixed population, whereupon the identity of most of the remaining L3 can be estimated in relation to those measured, without a need for further measurements. The keys were found to facilitate differential larval identification and are particularly useful for training.

Experimental Oesophagostomum bifurcum in monkeys.

OESOPHAGOSTOMUM BIFURCUM: larvae, cultured from human stools collected in northern Ghana, were used to establish experimental infections in monkeys. A patent infection was established in a rhesus monkey (Macaca mulatta) and this infection was used to generate larvae to inoculate additional monkeys. In all, 17 animals were inoculated. Thirteen of 15 animals developed antibodies to the infection between 19 and 62 days post inoculation (PI); two animals had a positive response before inoculation. Four of ten animals developed patent infections between 88 and 134 days and passed eggs in the faeces. Egg shedding was consistent in only one animal, but at low levels of one or two eggs per 2 mg direct smear, and extended over a 400 day period. In the other three animals, egg shedding was sporadic and of only 2-4 weeks duration. In seven animals necropsied between 19 and 22 days PI, one to 17 early fourth-stage larvae were recovered from nodules in the bowel wall; in an eighth animal examined at 314 days, six immature adult worms (early fifth stage) were recovered from nodules in the bowel wall. The morphological features and growth of these recovered larvae are described. Three animals were inoculated with larvae that had been dried for one week at 28 degrees C; two animals began shedding eggs at 128 and 134 days PI, respectively. The present results suggest that the parasite obtained from humans is poorly adapted to lower primate hosts, and supports the concept that Oesophagostomum bifurcum found in humans and monkeys in the same geographical region of northern Ghana and Togo are distinct and that the infections in humans are not likely to represent zoonotic infections acquired from monkeys.

Differentiation of two Oesophagostomum spp. from pigs, O. dentatum and O. quadrispinulatum, by computer-assisted image analysis of fourth-stage larvae.

A method was developed to differentiate between fourth-stage larvae (L4) of two species of porcine nodular worms, Oesophagostomum dentatum and O. quadrispinulatum, by computer-assisted analysis of digitised microphotographs of L4 grown in vitro for various time periods and of L4 ex vivo. The overall lengths of the larvae and the lengths of the oesophagus as well as parameters describing the shape of the oesophagus and buccal capsule were measured and a formula based on these parameters was developed that could differentiate between the two species on the basis of the morphometric data. It was demonstrated that morphometry can produce unbiased data which can be employed for the calculation of indices suitable for the differentiation of morphologically different specimens. Computer-based techniques facilitate the processing of the complex data and offer the option for automation of measurements for routine applications.

Experimental hybridization between Oesophagostomum dentatum and O. quadrispinulatum in pigs.

To investigate eventual hybridization between two nodular worm species of pigs, Oesophagostomum dentatum and O. quadrispinulatum, we used either mature, adult worms or 10-day-old fourth-stage larvae (L4) as starting material, employing a nonsurgical transplantation technique. Following the transfer of adult worms the ensuing first generation of larvae gave rise to adult worms that were found by morphological examination to be purely O. dentatum. Therefore, we decided to use the immature L4 as starting material. After the transfer of L4 to recipient pigs, fecal cultures were established and the L3 derived from the O. dentatum male O. quadrispinulatum female cross gave rise to adult but infertile worms, which morphologically had the sexual characters of their parent generation, whereas other characteristics were intermediate between the two species. Attempts to reproduce the hybrid worms or the reciprocal cross were unsuccessful, indicating that hybridization between the two species is a rarely occurring phenomenon.

Observations on the morphology of adults and larval stages of Oesophagostomum sp. isolated from man in northern Togo and Ghana.

Infection with Oesophagostomum sp. appears to be extremely common in man in northern Togo and Ghana. Adult specimens were recovered from the intestinal lumen by treatment with pyrantel pamoate and the morphological characteristics of oesophagostomes of man could for the first time be compared with information available on the morphology of oesophagostomes of monkeys. The observations and measurements demonstrated that the species involved is Oesophagostomum bifurcum and that the eggs of this species cannot be differentiated from those of Necator americanus. Both infections occur simultaneously in the population involved. The L1 larvae, too, cannot be differentiated from hookworm L1 larvae. The L3 larvae, however, are characteristic. Diagnoses of human Oesophagostomum infections is based on the detection of these larvae in coprocultures. In the present paper, the eggs, the L1 and L3 larval stages and the adults, are carefully described and photos are given.

Oesophagostomiasis in man: report of the first Malaysian case with emphasis on its pathology.

This paper describes the first Malaysian case of oesophagostomiasis. The patient was an 8-year-old Malay boy who presented to Ipoh General Hospital, Perak with abdominal pain and weight loss. Examination revealed multiple cavitated pseudotumours of the colon. A hemicolectomy was performed. Examination of the lesions revealed Oesophagostomum worms in the necrotic centres. The differential diagnoses and the pathology caused by Oesophagostomum are discussed. A brief review of the available literature is presented.

Parasites of South African wildlife. V. A. description of the males of Oesophagostomum mocambiquei Ortlepp, 1964 from warthogs, Phacochoerus aethiopicus (Pallas, 1766).

Oesophagostomum mocambiquei Ortlepp, 1964 was described from 9 females recovered from a warthog, Phacochoerus aethiopicus (Pallas, 1766), from northern Mozambique. Large numbers of O. mocambiquei were recovered during subsequent surveys of the parasites of warthogs from the Kruger National Park and the Hoedspruit Nature Reserve. The males, which have not yet been described, resemble those of Oesophagostomum santosdiasi Ortlepp, 1964 in the principal measurements. They can, however, be differentiated by the shape of the mouth capsule, which is round in O. mocambiquei and oval in O. santosdiasi. A simplified key for the identification of the Oesophagostomum species that occur in warthogs in South Africa and Namibia is provided and the differences between them tabulated. The names Oesophagostomum moçambiquei and Oesophagostomum santos-diasi are corrected to O. mocambiquei and O. santosdiasi respectively, since diacritic marks are not allowed under the Code of International Zoological Nomenclature.

[Species of Oesophagostomum in sheep and goats in Stara Zagora District]. / Vidov sustav na ezofagostomidite po ovtsete i kozite v Starozagorski okrug.

The study of small ruminant animals in the district of Stara Zagora has revealed that only one species of the Oesophagostomum genus could be found--Oesophagostomum venulosum (Rudolphi, 1809), Railliet et Henry, 1913. There are some morphological and metrical differences in the imaginal and larval stages between this species found in sheep and goats and the one described in the literature. It seems, therefore, that there exists great plasticity of these signs, and this should be taken into consideration in the identification of the species belonging to this genus.

Nematodes parasitizing domestic ruminants in Afghanistan.

A total of 12 nematode species were determined in the collection recovered from domestic ruminants in Afghanistan. Ten of them were found for the first time in this region: Trichocephalus globulosus, Trichostrongylus probolurus, Cooperia bisonis, Nematodirus spathiger, N. abnormalis, Thelazia rhodesi, Bunostomum phlebotomum, Haemonchus contortus, Dictyocaulus filaria and Oesophagostomum radiatum. Morphological and metrical characteristics of T. globulosus, T. skrjabini and C. bisonis, based on our own material, are added.