Faecal egg count helps but won't reveal pre-patent hoose

Veterinary advice on treating parasites in cattle
Faecal egg count helps but won't reveal pre-patent hoose
A vet takes a break from fertility testing a dairy cows.

The time has come and gone when I used to go out to deliver the Knowledge Transfer scheme to those clients who had signed up for it.

A lot of these clients took up the option of parasite control as their extra choice.

This option was introduced in order to highlight the resistance that had become apparent in relation to anthelmintics. Farmers had found that, despite the use and continued use of wormers, they still had coughing and scouring among their calves. Every year we see similar problems with calves.

Recently, we sent a calf to the Regional Vet Lab in Model Farm Road, Cork, that had apparently died suddenly out in the field.

The result came back that this calf had all the post-mortem symptoms of pre-patent hoose.

How does this differ from ordinary hoose, you might ask?

When the infective larval stage is swallowed by the calf, it goes on a journey through the body, and through different stages of development, it ends up in the lungs of the calf.

In the lungs, the lungworm matures into the adult stage and starts the process of producing young larvae which are coughed up, swallowed and passed out in the dung. As the amount of larvae that are produced increases, so does the level of coughing that the farmer hears.

The time taken from the ingestion of infective larvae to production of new larvae is called the patent period, and is usually put at three weeks.

Sometimes, the calf takes in massive amounts of the infective stage of the lungworm, and when these reach the lungs, the reaction that is caused results in what is known as pre-patent hoose.

This means the length of time from ingestion of the infective larvae to the appearance of problems is less than the normal three weeks.

The reaction by the calf’s lungs is such that an enormous amount of mucus is produced to combat the invader, and this essentially floods the lungs, and the calf finds it next to impossible to breathe.

In an outbreak of pre-patent hoose, it is not uncommon to see a number of deaths.

As part of the Knowledge Transfer scheme, we were pointing out the value of doing faecal egg sampling. This can be carried out at a few times of the year.

Firstly, it can be done to find out the level of larvae (gutworm, lungworm, and liver fluke) throughout the summer season, and thereby gauge the need for dosing.

As pre-patent hoose occurs before the lungworm has reached its adult stage, there will be no sign of lungworm larvae in the calf’s faeces.

Therefore, relying solely on the results of a faecal egg count can be very dangerous.

Herdowners need to be on a constant watch out for the first signs of coughing in young calves.

It can also be used to find out the effectiveness of the dose that has just been used. If the faecal egg count (FEC) is done exactly 14 days after any type of dosing (oral, injectable, or pour-on) then there should be no larvae in the dung.

This FEC will tell us if a resistance has been built up towards the wormer used.

There are basically three families of wormer. These are Benzimidazoles (Albex, Fenben, etc); Levamisoles (Panacur, Levicide etc); and the Mectins (Ivomec and all the other pour-ons and injectibles). Farmers need to be in constant communication with their vet regarding the type of dose to be used, and how often it should be used.

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