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Parasite paradise

Barber’s Pole worm in alpacas. By Sue Thomas.

Humid air, moist grass and mild temperatures are ‘party central’ for the enemies of alpacas – gastrointestinal worms. More alpacas die through parasitic infestation than virtually any other single cause, yet owners often find it difficult to spot the signs of infestation, and improve husbandry to reduce the effects.

Many nematode worm species occupy sections in the gastrointestinal tract of your alpacas. From mouth to rectum is a warm, moist, dark space, perfect for feeding, growing and reproducing. Consider it from the worms’ perspective, life could not be better, tucked away with constant warm temperature, food and protection at no cost to them.

Of course, as in all ecosystems, and the digestive tract of your alpacas is an ecosystem, there will be competition between worms for the best ‘pitch’. Different species of worm favour different spaces within the tract. The worm must avoid immune responses of the host but in the main the gut is a very hospitable place for worms to survive, hence their success. These insidious parasites share a common objective; to shelter, grow and reproduce within their host, bringing nothing to the party whilst taking all they can.

Which alpacas are at risk?

Before starting to tackle any gastrointestinal parasite problem on your farm there are a few helpful basics. Parasitic worms are not spread evenly in your herd rather populations aggregate or clump together with the majority of the parasite burden carried by only 10% of your herd.

A history of good nutrition and health puts alpacas in the best position to defend against invading worm larvae

Young stock, the nutritionally challenged and animals under stress are particularly vulnerable. A history of good nutrition and health puts alpacas in the best position to defend against invading worm larvae. When exposed to infective parasites, some alpacas simply don’t get sick. They may have built a strong immunity, so can keep the parasites at bay.

The majority of worm parasites develop on pasture, waiting to be ingested by animals to complete their life cycle. If you treat your alpacas with ‘dewormers’ or anthelmintics on a regular basis, it is likely that you are unnecessarily treating the majority of your herd, wasting time and money, but worse, building the likelihood of anthelmintic resistance, now common in sheep flocks around the world.

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Parasite challenge

So here is the parasite challenge…to identify the alpacas carrying high parasite burdens and treat effectively to minimise contamination to others, without compromising future herd health by encouraging anthelmintic resistance.

Barber’s Pole worm

Haemonchus Contortus

A key player in the gastrointestinal parasite team is the Barber’s pole worm (Haemonchus contortus). The worm is so named as the adult females display white ovaries which spiral around a red, blood filled intestine, giving the appearance of a traditional Barber’s pole. Performing faecal diagnostic services for alpaca keepers, and in my research on internal parasites of alpacas, I have seen a huge rise in both owner concern and the presence of H. contortus. As there are few obvious clinical signs (particularly the absence of diarrhoea) alpaca death may appear sudden, although infection of your alpaca may have been prolonged. The mild, wet weather plays a key role in the worms’ success. It is helpful to understand how.

Life cycle

An adult female Barber’s Pole worm, residing in the third compartment of the alpaca stomach, can produce up to 10,000 eggs per day in contrast to other worms of the digestive tract which typically produce only 100

The life cycle of Barber’s Pole worm is direct (requires only one living host) and has an ‘in-host’ and environmental phase. The environmental phase of the life cycle presents the most danger and loss of resource to the worm population, a problem this species overcomes with a huge egg producing capability. An adult female Barber’s Pole worm, residing in the third compartment of the alpaca stomach, can produce up to 10,000 eggs per day in contrast to other worms of the digestive tract which typically produce only 100.

Eggs are shed on to pasture in faeces where heavy contamination can soon build up. The faecal pad plays an important role as the incubator for eggs and food source for hatched larvae. The egg has a hard shell with the moist sanctuary of the faecal pad (alpaca faeces comprise 87-90% water at voiding) providing a perfect environment for egg development. Prolonged summer sunshine can dry the faeces and desiccate the eggs, reducing viability.

Hatching

Eggs hatch releasing worm larvae known as the first larval stage or L1. Larvae then begin to move from faeces to pasture. Larvae can move up to 5-10cm horizontally from the faecal pad where moisture is available. They shed their outer cuticle to reveal second stage larvae which continue to move from the faecal pad, feeding on bacteria whilst growing.

Research as long ago as the 1950’s demonstrated that Haemonchus contortus larval migration from a batch of sheep pellets kept at 14.5OC continued for over 50 days, in optimum conditions. Much of the data on Barber’s pole comes from the sheep industry, where this worm is responsible for huge economic losses worldwide. A great deal of research information has been assembled from sheep and lambs in South Africa and Australia, but this should be interpreted with care when considering alpacas in the UK.

Sheep faecal pellets are typically smaller and individually discrete when compared with alpaca faeces, which are generally larger, formed from hundreds of pellets as a mass. This will have an effect on the speed of egg desiccation in sunlight and the degree of humidity available for egg development and larval migration.

Identification of eggs

It is worth noting that the presence of eggs in a faecal sample is not enough to identify Barber’s Pole worm. I have had many conversations with alpaca owners, frustrated that their vet or lab can’t give an immediate positive diagnosis from a faecal sample even when worm eggs have been found. The Barber’s Pole worm egg looks very similar to many other worm eggs in the Trichostrongyle group of nametodes. Detailed measurement of dimension and structure may be made (morphometrics) but the only method of achieving positive identification is to incubate and hatch the eggs, then grow on to the infective larval stage (see below).

Infective larvae

A second moult to L3 follows and the resultant third stage larvae or L3 are now on the pasture, moving across the ground and up blades of grass. A significant difference between the infective L3 stage and earlier stages is that the L3 is non-feeding, the mouth cavity being covered by a skin or sheath.

These larvae are now on borrowed time. They must survive on accumulated food reserves. Larvae move from ground level up on to grass in moist conditions and are attracted to mild sunlight. Strong sunlight repels the larvae back towards the ground. Heavy rain can wash larvae down to the soil but they can be ingested with drinking water taken by alpacas from puddles on the ground.

Moisture is required for upward movement on grass. Even in a very dry spell of weather; early morning dew will contribute to the cooler, wetter micro-climate at the base of the sward. Rapid larval development in warm, humid conditions can lead to a dramatic onset of disease as the infective larvae are eaten by grazing animals.

Juvenile worms

Once ingested, the worm sheds the mouth covering sheath becoming a juvenile or L4 stage larva. In as little as six hours, the juvenile worm migrates to C3 (third stomach compartment) where it begins to feed. It penetrates the gut lining with a sharp lancet in its mouth cavity and draws blood from the unsuspecting host.

A faecal sample taken for analysis at this stage will fail to reveal Barber’s pole worm as the juvenile stage is not capable of reproducing and shedding the vast number of eggs of the adult worm. It does however feed on blood and can begin the debilitating ill-thrift and anaemia that characterises haemonchosis. This means that a negative faecal egg count shouldn’t rule out the presence of Barber’s Pole worm, be vigilant and if in doubt repeat the egg count in a few days.

Blood sucking adult

The fourth stage juvenile moults for a final time to become a mature Barber’s Pole worm moving across the lining of C3, latching on with its mouth, lacerating the mucosa with a lancet and sucking blood from capillaries. The worm changes feeding station, releasing its hold to find a new position in C3, leaving a damaged mucosa which continues to seep and bleed.

An alpaca infected with 10,000 Barber’s Pole worms may lose up to 500ml of blood per day

Observations on bleeding caused by Barber’s Pole worm in sheep recorded that bleeding often continued for more than 7 minutes following the worm’s move to a new site. Each worm will remove around 0.05ml of blood per day, either by direct ingestion or loss to the gut as the worm moves around and re-penetrates the gut wall. An alpaca infected with 10,000 Barber’s Pole worms may lose up to 500ml of blood per day. Blood can be replaced by manufacture of new cells but bone marrow soon becomes exhausted.

Protein loss

Protein loss into C3 from parasitic damage can lead to oedema as water in drawn down into cellular spaces. This is often noticeable by swelling in the lower jaw area, a sign known as ‘bottle jaw’. Feeding female worms now reproduce shedding thousands of eggs each day, perpetuating the cycle of parasitic infection and pasture contamination. This is of particular concern when cria, with immature immune systems, are beginning to graze. Pasture management is important to parasite control systems. Remove faeces where possible or move alpacas onto fresh or ‘safe’ ground as often as possible, particularly if stocking density is high.

Treating an entire herd with anthelmintics, whether or not they require treatment, may build resistance to drugs over time. This could mean that when you really need to medicate, drugs may not be effective. A targeted approach to treatment is preferable. That is why identification of any ‘wormy’ alpacas is so important.

Spot the signs

Behaviour
The farmer’s eye is the best guide to a change in alpaca behaviour. A depressed attitude, lack of appetite, slow to the trough and lagging behind the herd should be investigated. There could be many causes and parasitism should be ruled out.


Weight
An alpaca with a heavy burden of Barber’s Pole worms loses weight and condition quickly.

An alpaca 1 day before death which was confirmed at post mortem as H. contortus infestation

Regular weighing or as minimum, body condition scoring is important. These photos clearly demonstrate the effects of parasitic disease. These female alpacas are the same age and had similar weight profiles. Although on the same pasture one alpaca lost weight (14kg), had a high worm egg count (>1200epg mixed burden including H.contortus) and became anaemic. Treatment with anthelmintic, daily dosing with supplementary feed containing vitamins and minerals slowly led to recovery. Regular body condition scoring was a useful indicator of her progress.


Anaemia
Membranes of the eyes become very pale as anaemia increases. A scoring system based on the degree of red colouration of the membranes of the eyes has been developed as an on-farm test suggesting the presence of Barber’s Pole worm through associated anaemia in sheep.

This test, known as FAMACHA©, developed originally for control of H. contortus in sheep and goats indicates (on a 1-5 colour scale) the level of anaemia resulting from blood loss. The 1-5 colour scale has been correlated in sheep with packed cell volume; an indication of anaemia, and forms a basis for treatment strategies. I have trialled FAMACHA© in research with alpacas and found it a useful tool but not in isolation as the calibration of membrane colour to packed cell volume in alpacas has not been validated.

Checking membranes for colouration, salmon pink is good on the FAMACHA© scale and requires no treatment

FAMACHA© is not a stand-alone system but should be used as part of a strategic worm control programme. As with most on-farm control systems, successful use of the FAMACHA© scale increases with experience as the farmer develops expertise each time the herd or flock is benchmarked. Caution must be exercised, as anaemia can result from many conditions, other than infestation with H. contortus. But it is worth getting to know the look and colouration of your alpacas’ eye membranes (usually a bright pink/salmon red colour) so that you can spot anaemia in its early stages.


Faecal eggs counts
Faecal egg counts (FEC) can increase dramatically when Barber’s Pole is present, although sometimes this is recognised too late to be of use in treatment. However identification of the main worm egg shedders in your herd is useful, both for targeting treatment and decision making for breeding purposes. No-one wants a ‘wormy’ stud that may pass ‘wormy’ genetics across your developing herd.

Diagnostic faecals for parasitic identification and count can be performed by your vet, or by labs such as my own. Training to perform FEC’s on your own farm is perfectly achievable with relatively low costs through an on-farm set of simple laboratory equipment. I have trained many alpaca keepers over the last few years who now test their alpacas and get a same day result, allowing confident, faster and effective treatment. Do contact me for more details of training to perform your own ‘on farm’ egg counts.


No diarrhoea
Unusually with an alpaca stricken with H. contortus, there is NO diarrhoea. This confounds most alpaca owners as gastro-intestinal parasitism is often associated with diarrhoea or ‘scouring’. Barber’s Pole worm infestation is in the stomach rather than the intestine so the alpaca often produces firmer faecal matter with no tell-tale staining or diarrhoea. I have seen alpacas displaying weakness, lagging behind the herd, weight loss, anaemia and constant diarrhoea, which at post mortem were diagnosed with very high levels of H. contortus. Other worms present may have caused scouring. Remember that gastro-intestinal parasitism is rarely a single source of infection. So if in doubt, always check faecal and seek veterinary advice.

SUMMARY OF SIGNS

Behaviour: are there any alpacas lagging behind the rest, slow to feed, always at the back of the group trying to keep up? Are there cria spending too long sitting down, slow to feed and away from their dam?

Weight loss: if you don’t routinely weigh your alpacas, get close and handle them and note down the body score. What looks like a healthy alpaca from a distance could be emaciated under the fleece.

Anaemia: if in doubt check the membranes or ask your vet to run a blood test.

Faecal egg counts: a fast route to a snapshot of the gastro-intestinal scene. Record and repeat faecal egg counts on any alpacas with high eggs per gram (epg). Look for trends which indicate a problem and promote strategic worming. FEC’s also give accurate knowledge of the parasites present allowing you and your veterinarian to select the most appropriate anthelmintic product. Gastrointestinal parasitism is rarely a single species.

Physical signs: swelling under the jaw known as ‘bottle jaw’ may be present.


Avoid the traps

Don’t overgraze an area or keep alpacas at too high a density. It is not just the number of alpacas per acre but your management strategy on that acreage, do you collect faeces from the pasture?

Don’t be fooled into thinking a very thin dam is only thin because she is feeding a cria. If she is lactating and is very thin, increase her ration and check faecals for worm eggs.

Don’t perform faecal analysis on pooled samples as the majority of worms in your herd are carried by a small percentage of animals. Find out who the shedders are and treat accordingly. This will help to maintain untreated worm parasites in your herd and reduce the possibility of anthelmintic resistance.

Don’t bring newly acquired alpacas directly into your herd. Quarantine new alpacas for a minimum of four weeks; taking FEC’s on arrival and prior to release into the herd. This will ensure that any parasites from other farms are not distributed to your herd.

If in doubt – call for your vet.

Sue Thomas runs the Lyme Alpacas herd of alpacas based in Lyme Regis, Devon. Sue offers parasitology courses for alpaca keepers who want to perform faecal testing on their own alpacas. (www.lymealpacas.co.uk). She is currently part of the Infection and Immunity Group at the Royal Veterinary College in Hatfield. Her PhD research is investigating endo-parasitic interactions of South American Camelids. If you are interested in learning more or contributing to this research by periodically providing alpaca faecal samples for analysis, please contact Sue for more details. Email: suthomas@rvc.ac.uk or mobile 07887 511774

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