CASE NOTES


The Haemonchus Dipstick Test—Detecting Barbers Pole Worm Infection in Sheep

Mark Doherty, Technical Services Manager, Ancare Australia Pty Limited

Posted Flock & Herd August 2010

INTRODUCTION

The Haemonchus Dipstick Test has been developed by the Cooperative Research Centre for Sheep Industry Innovation (Sheep CRC) as an on-farm decision support tool to help farmers decide when to treat for Barber's Pole worm infection. The test is rapid and relatively inexpensive, and can be used regularly by producers to assess the level of Haemonchus contortus infection in different mobs of sheep. The practical application, methodology, benefits and limitations of the test are briefly described.

BARBER'S POLE WORM INFECTION

Barber's Pole worm (Haemonchus contortus) is a nematode parasite of the abomasum of sheep and other ruminants. Adult and immature (L4) Barber's Pole worms feed on blood. The high fecundity of the worm, its relatively short lifecycle and its ability to proliferate in warm, wet conditions means infections can develop rapidly in certain environments.

Acute infection with large numbers of infective larvae can result in disease outbreaks in affected mobs prior to the production of significant numbers of eggs by adult worms. Sheep affected by Haemonchosis present as dehydrated, anaemic and hypoproteinaemic. Deaths are often seen in affected mobs.

TEST DEVELOPMENT AND APPLICATION

The Haemonchus Dipstick Test relies on guaiacol-based reagent test strips to detect haemoglobin in dung. The test is therefore an indirect test and results must be interpreted with consideration of other factors including the time of year, paddock history, climate and drench history of the test mob. The amount of haemoglobin detected in dung from infected sheep has been shown to correlate with the level of Haemonchus contortus infection.

Furthermore, as significant blood loss occurs 11 days after infection with larval Barber's Pole worm (approximately seven days prior to egg production) the test can be used to help detect early infection prior to detecting significant worm egg counts.

METHODOLOGY

The Haemonchus Dipstick Test is conducted on fresh dung samples collected from the ground rather than per rectum. Rectal samples are not suitable as they may be contaminated with blood from rectal mucosal bleeding during sample collection. A pooled dung sample representative of the mob should be collected. This generally means pooling a collection of approximately 20 pellets from 20 separate dung pats.

The test consists of a step-by-step process of precise dilutions and a boiling step. Strict timings must be adhered to for consistent results. Once a test solution of the correct specifications is produced, a reagent stick is used to assess the amount of haemoglobin present. The stick's colour change is compared to a graduated scale. Results are interpreted by comparing the score obtained to a series of standard scores.

BENEFITS OF THE TEST

Some of the key benefits of the Haemonchus Dipstick Test include:

LIMITATIONS OF THE TEST

Training in use of the Haemonchus Dipstick Test is strongly recommended prior to its use. Strict timings and procedures must be adhered to for reliable results. Training courses conducted by rural produce merchandisers and pharmaceutical company representatives provide producers with the necessary background and practical training.

Considerations prior to using the test include:

In summary, the Haemonchus Dipstick Test is a rapid, indirect, on-farm decision support tool for helping farmers decide when to treat their sheep for Barber's Pole worm. The test can be purchased through rural produce merchandisers throughout Barber's Pole endemic areas in Australia.

REFERENCE

  1. Colditz I, Le Jambre L. Development of a faecal occult blood test to determine the severity of Haemonchus contortus infections in sheep. Vet Parasitol 2008;153:93-99

 


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