Two studies offer differing assessments of the value of garlic in worm control in horses.

Garlic is said to have many beneficial properties and is often fed to horses. Supplements claim benefits including anti-septic, anti-inflammatory and antibacterial effects, as well as acting as a fly repellent and appetite stimulant.  Garlic is also said to act against intestinal parasites.

There is a worldwide problem of drug resistance in nematode (roundworm) populations, which has led to a growing interest in alternative methods of control.

Garlic formulations are often used in prevention and treatment of intestinal parasites. But are the effective? Recent reports have produced conflicting evidence regarding the effect of garlic against strongyle nematodes.

Mousa Tavassoli and colleagues at the Faculty of Veterinary Medicine, Urmia University, Iran conducted a study of the anti-parasitic effects of hydroalcoholic extracts of garlic (Allium sativum) and Ferula asafoetida (a plant native to the area that has been used to treat intestinal parasite infections in traditional medicine).

Third stage strongyle larvae were exposed to different concentrations of extracts of both plants and to tap water.

The researchers found that both garlic and Ferula asafoetida extracts were effective against the larvae, demonstrating dose-dependent anthelmintic activities. Larval mortality rate increased significantly as the time of exposure to the extracts increased.

They conclude that hydroalcoholic extracts of F. asafoetida and A. sativum have potential anthelmintic and larvicidal activities in vitro. They suggest that further in vivo evaluation of the different parts and fractions is needed to make use of these plants for beneficial purposes.

On the other hand, a study in Italy assessed the effect of garlic on egg-shedding and found that garlic failed to control intestinal strongyles in naturally infected horses.

Francesco Buono and colleagues monitored the effect on egg shedding in horses naturally infected with intestinal strongyles.

The field trial was conducted in a horse trotter farm in Southern Italy. Fifteen naturally infected mares were allocated to one of three treatment groups:

 

• fresh garlic group – animals received 40 g of fresh crushed garlic once daily for 15 days;
• dry garlic group – animals received 40 g of commercial dry garlic flakes food supplement once daily for 15 days;
• control group – no treatment

 

After two weeks of garlic administration, a faecal egg count reduction test showed the garlic failed to reduce strongyle egg shedding.

Long term administration of garlic has been associated with anaemia. However, in this study, red blood cell counts remained within normal limits throughout the treatment period.

They conclude: “In our study model, the oral administration of garlic formulations has no effect on reducing the egg shedding of intestinal strongyles, and the garlic supplementation over a short period of time is not responsible for hematological changes in horses.”