Gut Health Update: Coccidiosis control trends in Europe

Coccidiosis is like an iceberg. The clinical 10 per cent you see is bad
and makes it easy to forget that there is another 90 per cent (subclinical) down there somewhere.

Coccidiosis is like an iceberg. The clinical 10 per cent you see is bad
and makes it easy to forget that there is another 90 per cent (subclinical) down there somewhere.

But producers forget about the subclinical 90 per cent at their own economic peril, Maja Marien, technical manager of poultry in Europe and the Middle East for Alpharma, told veterinarians, government and industry officials and producers in Kitchener in October.

Marien said that subclinical disease damages birds’ enteric epithelial cells resulting in the reduction of nutrient absorption and less performance. Coccidia replicate by moving into the intestinal cells. The next generation of coccidian burst the cells’ walls to free themselves and in the process do extensive damage to the gut. Even a small number of parasites can damage the bird, affect how it performs and result in
economic losses.

Subclinical coccidiosis is also a predisposing factor for Clostridium perfringens.
Damage to the poultry industry in the United Kingdom in 1995 was estimated at 38.6 million pounds Sterling. It is estimated that 46 per cent of these costs came from reduced weight gain and 34 per cent from poor feed conversion.
“It’s a problem, an economic problem most of all,” she said.

Tools to deal with coccidiosis include vaccines, herbal products and anticoccidial drugs.
In the EU vaccines are a limited option. There are currently no vaccines registered in EU for turkeys. For chickens there are live attenuated or live unattenuated vaccines. Live
unattenuated vaccines are not registered in the EU and other vaccines are not frequently used in broilers in the EU.

A couple of problems are the price and the perception there are more bacterial enteritis problems compared with anticox, she said.

Another possible problem is that the species is in the field but not in the vaccine, e.g., E. mitis.

Herbal products are being touted by some as an alternative to traditional treatments. The anticoccidial sensitivity test (AST) evaluated five herbal products with claimed anticoccidial activity, she said.

“None of the herbal products proved to be efficacious,” she said.
However, Alpharma keeps testing and screening.

Anticoccidial drugs fall into two broad classes: chemicals and ionophores.

They are effective but work differently and there are issues such as increased resistance.
“After some time of use the efficacy of anticoccidials decreases,” she said.

Cross-resistance is also a concern with ionophores.

“If resistance to one product arises other similar products will also work less efficiently,” she said.

Chemicals all have very different targets to kill parasite and there is no occurrence of cross-resistance.

Ionophores, however, have a common mode of action and cross-resistance can be a problem.

However, there are big differences between ionophores of different classes and the implications for cross-resistance.

The way to prevent the development of resistance or cross-resistance is the use of a rotation program. This involves changing the anticoccidial drug to one of another class after a few cycles. This can be in shuttle or a full program, she said.

Rotation allows the restoration of anticoccidial efficacy and limits the buildup of resistance.

“After using an ionophore, do not use it (or any other ionophore from the same class) again for at least six months,” she said.

Limit use of a particular chemical to once a year – so if used three months in full, give nine months’ rest.

Ionophore and chemicals: use for up to six months and then give six months of rest.
The reason is that immunity plays a more important role in turkeys, she said.
Vaccines can also play a role in the rotation as they result in a faster restoration of sensitivity to the other treatments.

AST tests in broilers have shown that using a higher dosage can result in better coccidiosis control and will often pay off with improved bird performance that more than offsets the additional treatment costs.

Alpharma does lesion scoring during necropsy sessions in the EU to get an idea of coccidiosis control. The company also scores “bacterial enteritis / dysbacteriosis,” she said.

“Bacterial enteritis (BE) is one of the main health problems in EU poultry production,” she said.

Treatments for BE are standard practice in the EU, she said.

A lot of factors are involved in BE including diet and management, but there is also a close relationship with (sub)clinical coccidiosis as a predisposing factor.

The clinical signs of bacterial enteritis include: wet litter; diarrhea; stable instead of increasing feed intake and an increased water/feed ratio.

Necropsy shows: fragile, thin, transparent gut; dilated blood vessels; excessive fluids in small intestine; ballooning of intestinal wall; undigested feed.

Necrotic enteritis is rather rare in the EU compared with BE and has the same contributing factors as BE but mortality can range from five to 50 per cent, but is usually 10 per cent, she said.

Tools for prevention and treatment of bacterial enteritis/necrotic enteritis include therapeutic antibiotics such as amoxicillin, linomycin and tylosin. Such treatments are standard in European production, she said.

As an NE treatment, it is hard to beat amoxicillin, she said. It is very rapid and very efficient.

Alternatives such as Alphaflor can help. Tests show lowered mortality and lower percentage of NE positive birds. But there is no antimicrobial action.

In Europe there are no growth promoters allowed.

Meanwhile, however, it is estimated that 50 per cent of flocks in the EU
are treated at least once for bacterial enteritis.

As a consequence, you can’t underestimate (subclinical) coccidiosis as an instigator of bacterial enteritis.

Maintaining anticoccidial efficacy is very important in the prevention of other conditions especially in European conditions, where there is no fall back on 3-Nitro, growth promoters.

It is believed that many European producers use light doses to cut the cost of the treatments, but the cost to bird performance may be high. It is important that appropriate dosages be used as light dosages can result in the rapid development of resistance, more subclinical coccidiosis, more damage to the gut, less bird performance and increased economic loss.

In the same vein, rotation is essential in order to avoid resistance and reduced sensitivity.

Cleanup by using chemicals could boost performance, especially when the coccidiosis challenge is heavy.

Producers should use all the tools available for the future control of bacterial enteritis and coccidiosis. These include ionophores, chemicals, vaccines, therapeutics, and alternatives if they are shown to be effective.

They must also remember that they are not only dealing with the 10 per cent of the problem they can see, but the 90 per cent they can’t.