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RVL update on disease caused by roundworms, September 2019



Background

The mild and damp weather conditions found in many parts of the country during August would be expected to give rise to large numbers of parasite eggs and/or larvae on pasture. Recent cases detected in the Regional Veterinary Laboratories (RVLs) suggest that the level of pasture contamination with parasites is indeed high. A large number of cases with high parasite worm egg counts in samples of faeces have recently passed through the RVLs. While most gut worms are invisible to the naked eye, higher egg counts are generally associated with more severe infestations, which can cause production losses. 

 

Details of cases submitted to Kilkenny RVL

Two weanlings from one herd were diagnosed with hoose pneumonia (lungworm) in the last week of August. The carcases had been submitted with a history of severe respiratory distress and grunting on the previous day.

 Lungworms were also noted in the airways of a weanling from a separate herd submitted in the same week. This animal was one of four weanlings from a group of forty-seven to have died with a history of poor thrive. In this case, the lungworms were not believed to be the cause of death. Necropsy and further testing revealed additional interesting information. The investigation disclosed liquid intestinal contents and a high strongyle egg count of 1350 eggs per gram, indicating a large burden of gutworms. 

 

Poor thrive was likewise the standout feature in the history of two lambs which were submitted to the RVL in the last week. The lambs had been treated with an anthelmintic on the day prior to death. Again, both showed signs of a substantial gutworm burden on necropsy. They had liquid intestinal contents and high strongyle egg counts of 6000 and 2350 eggs per gram, respectively.

 

Finally, two six-month-old dairy calves were submitted with a history of ill-thrift and scouring at grass, with the attending private veterinary practitioner querying “summer scour syndrome”. On gross post mortem examination, both carcases were in poor body condition and had severe ‘moroccan leather’ appearance to the abomasal mucosa (i.e. the lining of the fourth stomach). Samples of gut contents from the two carcases contained 2550 and 5050 strongyle eggs per gram respectively. The gross lesions are highly suggestive of Ostertagiasis, an infestation of roundworms which live in the fourth stomach of ruminants. The very high faecal strongyle egg counts provide further evidence for a diagnosis of ostertagiosis.

  

Conclusion

The mild weather of late summer/early autumn has given rise to substantial worm burdens in certain areas. The scale of the problem in animals and herds is not always readily apparent from the appearance of the animals involved. Farmers are encouraged to consider information from a range of sources, including engaging their vet to advise on faecal egg counts, to inform their decision making on treatment and control of roundworm diseases. Farmers are also encouraged to seek a referral from their vet to their local RVL to investigate the cause of deaths in their livestock.

 

Figure 1: Image of an Ostertagia ostertagi worm in microscopic view

Added 19.09.2019

 

 

Figure 2: Image of the interior of an abomasum (fourth stomach) from an animal infested with Ostertagia ostertagi worms

Added 19.09.2019

Species: Multi-Species
4:30 PM on Thu, 19 September