Oesophagostomum - Diagnostic Tests

Diagnostic Tests

A definitive diagnosis of Oesophagostomum infection is traditionally done by demonstrating the presence of the larval or young adult forms in nodules of the intestinal wall via surgical examination of tissue. The larvae usually found in tissues can be 500 nanometers or longer in length. With microscopy, one can identify the larvae based on the presence of somatic musculature divided into four quarters, along with a multinucleated intestine as well as an immature reproductive system.

Laboratory methods are of little use for Oesophagostomum diagnosis. It is virtually impossible to make a diagnosis based on microscopy of stool samples alone, as Oesophagostomum eggs cannot be differentiated from hookworm eggs, which are often found in Oesophagostomum endemic areas. The only way to differentiate between the two species of eggs is to perform coproculture, which allows eggs to develop to their stage three larvae, although this is both time consuming and unreliable. Immunoassay tests like ELISA that monitoring for increases in IgG4 antibodies can indicate tissue invasion by Oesophagostomum.

Recent advances, however, have allowed for less invasive and more accurate methods of diagnosis. The following is a review of three articles detailing the diagnostic use of PCR assays and sonographic imaging. Verweij, Jaco J., Anton M. Polderman, et al. “PCR assay for the specific amplification of Oesophagostomum bifurcum DNA from human faeces.” International Journal for Parasitology 30.2 (2000): 137-142. This study developed a molecular-based approach to diagnosing oesophagostomiasis caused by O. bifurcum in humans. Using genetic markers in ribosomal DNA, the researchers developed PCR assays to selectively amplify O. bifurcum DNA from human fecal samples. These assays achieved sensitivity ratings of 94.6% and specificity of 100%, suggesting that the PCR method could be a viable alternative to the long-standing methods of diagnosis as well as an opportunity to reveal more about the epidemiology of oesophagostomiasis.

Storey, P A, S Anemana, et al. “Ultrasound diagnosis of oesophagostomiasis.” The Brit. J. of Radiol. 73.867 (2000): 328-32.

Sonographic imaging and ultrasound were used to examine two cases of oesophagostomiasis in the Nalerigu hospital in northern Ghana. The technology allowed for the detection of intestinal and abdominal wall modules, as well as their size, type and location in the case of the ultrasound. Multinodular disease was representedby nodular colonic lesions and pseudokidney appearances, while the single-nodular Dapaong tumor had the appearance of an echo-free lumen surrounded by a defined but badly reflective wall. The ability to diagnose oesophagostomiasis via ultrasound can reduce the number of excessive invasive surgeries and put greater emphasis on chemotherapy.

Verweij, Jaco J, Eric A T Brienen, et al. “Simultaneous detection and quantification of Ancylostoma duodenale, Necator americanus and Oesophagostomum bifurcum in fecal samples using multiplex real-time PCR. (2007) Am. J. of Trop. Med. Hygiene 77 (4) 685-690

A multiplex PCR method was developed for simultaneously detection of A. dudodenale, N. americanus and O. bifurcum in human fecal samples. The method was tested on human fecal samples from an area in Ghana where co-infections with all three species are endemic. Results showed that the method was both highly specific and sensitive, attaining 100% specificity and sensitivities of 100%, 86.7%, and 100% for detection of N. americanus, O. bifurcum and A. duodenale respectively. Furthermore, cycle threshold values, which correspond to parasite-specific DNA load, correlated with measured intensity of infection as demonstrated in Kato-Kato smears. This PCR method could potentially elucidate species-specific transmission pathways of hookworm-like infections and improve monitoring of interventions.