Ag-note: Parasite Focus – Haemonchus Contortus

To kick off the next series of Ag-notes compiled by The Ohio State University’s AS 4004 class of 2019, I found it appropriate to hit a timely topic, parasites, especially with the previously wet and now hot and humid environmental conditions that many livestock and their producers are experiencing. Therefore, Animal Sciences students Kirsten McCollough, Kourtney Sprague, Jamie Summers, Kristi Lampton, and Hannah Whitaker chose to focus on a specific parasite that is continually becoming more difficult to manage for small ruminant producers raising sheep and goats on pasture – Haemonchus contortus.

Haemonchus controtus, or more commonly known as the Barber Pole Worm, is an internal gastrointestinal parasite that primarily attaches to the abomasum (4th compartment of the ruminant stomach). Once attached, adult worms have the ability to consume 0.05 mL of blood per day. Now you may be thinking, that doesn’t seem like much. However, depending upon the level of infection dependent upon the number of worms, death can occur quickly as a direct result of anemia.

Before we discuss how to manage these parasites within our animals and on our pastures, I believe that it is important to first discuss the life cycle of this parasite in order to ensure that we understand how infection is established within our livestock. A full outline of the parasite life cycle can be found in one of my most recent posts – Understanding Parasites on Pasture. In general, the life cycle for H. contortus developing from an egg to a mature and reproductive adult can take simply 21 days under ideal conditions and let me tell you, this year may not have been ideal for crops, but it certainly has been ideal for the reproductive cycle of parasites. In addition, adult H. contortus females have the ability to lay 5,000 – 10,000 eggs per day! It’s no wonder why infection can occur so quickly and rapidly.

So what if you suspect that your animals are infected with parasites, how can you check to be certain? According to Kirsten McCollough, Kourtney Sprague, Jamie Summers, Kristi Lampton, and Hannah Whitaker parasitic infection can be classified as either hyperacute, acute, or chronic. Hyperactue infections present with few or no symptoms. In general, hyperactue infections can cause death within one week. An acute infection presents with anemia, submandibular subcutaneous edema (aka bottle jaw), chronic infection, and weight loss. These types of infections should be easier to identify visually, but once these visual cues appear, the animal tends to be extremely anemic and treatment should be implemented immediately. Chronic infections on the other hand presents with sub-clinical signs such as abomasal inflammation leading to increased gastric secretions and tissue damage. Chronic infections can be identified via a field necropsy. If you as the producer do not feel comfortable performing this, call your local veterinarian to get an accurate diagnosis to ensure that you are making the proper management decisions to control parasites in your operation.

Now that we know some of the physical signs of infection, what are the tools that we have available to determine if our livestock may be parasitized before we have to rely on a high level of infection. As mentioned several times on our blog before, the FAMACHA © eye scoring system is an invaluable tool that any small ruminant producer can utilize when evaluating their flock or herd for infection potentially caused by H. contortus. For an excellent overview using this easy and efficient tool, be sure to check out Rory Lewandowski’s piece – Use FAMACHA Correctly. An additional tool that can be easily used on-farm also includes conducting a Fecal Egg Count test. For those interested in learning more about how to use both the FAMACHA © eye scoring system and how to properly conduct a Fecal Egg Count test, be sure to be on the look out next spring for our next session. For those interested in knowing more about what to expect for these courses, be sure to check out this year’s event flyer. On the other hand, if you would rather have a skilled professional conduct your Fecal Egg Counts, contact your local veterinarian. In addition, you could also request that they also take a blood sample to evaluate the packed cell volume (PCV – a measurement of the percentage of red blood cells) to determine the level of anemia.

At this point you may be thinking, “well how do I manage these parasites?” If recall my recent post on On-farm Parasite Management Strategies, there are several management strategies that can be implemented on-farm to manage parasites. In addition to those listed in my previous post, Kirsten McCollough, Kourtney Sprague, Jamie Summers, Kristi Lampton, and Hannah Whitaker also recommend that if lambing or kidding on pasture or in an area where transmission of parasites from dam to offspring is high, treating with an anthelmintic (de-wormer) 2 weeks prior to birth will decrease the number of eggs shed. In addition, regularly monitoring fecal egg counts too will give you as a producer a better idea of the level of infection within your flock or herd.

To conclude our discussion for the day, Kirsten McCollough, Kourtney Sprague, Jamie Summers, Kristi Lampton, and Hannah Whitaker wanted to leave us with some economic values to help us fully understand the negative consequences associated with parasitic infection. According to the USDA APHIS NASS report in February of 2019, the overall estimated loss as a direct result of parasitic infection for Ohio producers raising sheep in 2018 was approximately $485,000! Now this value may not truly represent the total number of sheep lost due to parasitic infection as some producers do not report their values or were able to attribute the loss of an animal to parasites. None the less, this figure shows the harsh reality of parasitic infection. Therefore, producers should continue to strive to continually monitor their flocks and herds for parasitic infection. Remember, there is no silver bullet for parasite management, thus implementing two or more parasite management practices is key.

Parasite Focus – Haemonchus Contortus
** Follow the link above to view the Ag-note.