HAEMONCHOSIS IN SHEEP AND GOATS : APPROACHES FOR ITS MANAGEMENT
Barber’s pole worm (Haemonchus contortus) is a blood-sucking roundworm of sheep and goats, with minor crossover into cattle. It has a typical roundworm life cycle in that its eggs are passed in a sheep’s faeces, hatch and moult three times in the environment to an L3 form which is infectious and eaten by a sheep. It then develops to an L4 and adult worm in the abomasum.
The contribution of livestock sector to Agricultural GDP is about 33 per cent. The livestock sector is one of the fastest growing agricultural subsectors in developing countries like India. The growth in demand for various livestock products has been showing an increasing trend in tune with population growth, urbanization and increasing income in developing countries. Sheep husbandry has been traditionally associated with many communities particularly belonging to small and marginal farmers in arid, semi-arid and mountainous area of the country due to its multi-faecet utility for wool, meat, skin and manure. It is easy to manage sheep along with cattle under semi-intensive system of rearing to their grazing capability that saves labour for which sheep rearing is preferred to goats in many parts of our country. Sheep & Goat husbandry provides a dependable source of income to the farmers through sale of wool and mutton. They play a significant role in the livelihood of small and marginal farmers and landless laborers engaged in sheep & Goat rearing. Like other grazing animals, sheep & Goat are also prone to parasitism with many ecto and endoparasites. The nematode class is one of the main causative worm parasites that causes economic losses in sheep/Goat production (Coop and Angus, 1981) . Amongst the different nematodes infecting sheep/Goat , nematodes of gastrointestinal tract are a major hindrance to production performance of sheep /goat throughout the world including India (Kumar et al., 2008) . Gastrointestinal nematodes in general and Haemonchus contortus in particular poses a serious threat to sheep/goat husbandry throughout the world. Haemonchosis is more a health problem in tropics and subtropics. Epidemiology of any parasitic infections which is variable with respect to breed, age, sex, geographical location, topography and climate plays an important role to understand the seasonality of parasitism and prepare region specific control measures. The clinical diagnosis of gastrointestinal nematodes is difficult, since the signs are not pathognomonic. However, diagnosis of the infections plays a major role in investigating epidemiology of the parasite. The ante mortem diagnosis of nematode infections in livestock, primarily, is based on the detection of nematode eggs or larvae in the faeces while quantifying of the egg per gram of feces is the best way of estimating parasite loads.
Haemonchosis is one of the most significant parasitic diseases of livestock worldwide, which is a main cause of production losses and ill-health in sheep and goats. This disease is caused by Haemonchus contortus (H. contortus), a nematode parasite of the ruminants’ abomasa. It is one of the greatest pathogenic nematodes, known as ‘barber’s pole worm or red stomach worm or wire worm’ of small ruminants, which inhabits the abomasum. The acute and emaciated form of disease is commonly seen in young animals, while adult animals are more resistant to infestation (Onyenwe et al., 2005). The common clinical signs are ascites, weight loss, anaemia, sub-mandibular edema, and death. Infection with H. contortus caused a significant reduction in the erythrocyte counts, haemoglobin concentrations and packed cell volume (PCV) and significant increased white blood cells (WBC) and eosinophil, also produce significant reduction in total protein, calcium and iron (Alam et al., 2020).
Haemonchosis affects sheep and goats of all ages at pasture. It can also affect cattle, however, unlike sheep and goats, cattle develop a level of immunity from 12 months of age.
Caused by the blood sucking parasitic worm Haemonchus contortus (aka barber’s pole worm due to its red and white striped appearance), haemonchosis is generally seen from mid-spring to autumn, when the temperatures rise allowing hypobiosed (dormant) larvae to emerge from the abomasal lining and mature to the blood sucking
adults. Warmer, wetter weather also lets the earlier (L3) stage larvae & eggs develop at pasture.
H.contortus adults are found in the abomasum where they latch on to the mucosa and suck blood. When they detach, the abomasal mucosa continues to bleed leading to severe anaemia and death. A single adult H.contortus can remove 0.05ml/day so infection with 5000 worms can cause 250ml of blood loss/day1. It is also important to note that females are prolific egg layers and can produce 5000-6000 eggs/day each.
Three types of haemonchosis exist:
- Acute: presenting with sudden onset anaemia +/- sudden death due to high worm burden and high blood loss. Often seen in young animals or animals with a low body condition score that cannot produce red blood cells fast enough to replace those lost.
• Sub-acute: Occurs when red blood cells are produced at the same rate as they are lost to the parasite, however this puts a drain on the bone marrow supply and often progresses to acute disease. As well as the chance of progressing to acute disease, sub-acute haemonchosis causes lethargy, slow growth rates and weight
loss.
• Chronic: Usually with a low burden where the affected individual(s) can produce red blood cells faster than they are lost to the parasite, although pallor and a low level of anaemia are often seen +/- weight loss due to the persistent protein drain. A ‘bottle jaw’ can be seen in some cases.
Unlike most small ruminant diseases caused by parasitic worms, diarrhoea is not a feature of haemonchosis.
The cause is Haemonchus contortus, known by a variety of common names, including Large Stomach Worm, Barber’s Pole Worm, Red Worm, Rennet Worm, and Twisted Wire Worm. The disease is an anaemia resulting from the vigorous blood-sucking activities of the worms. Symptoms identical with those seen in severe haemonchosis can be produced by bleeding sheep from the jugular vein to the extent of 200-600 c.c. daily for about three weeks.
The predisposing causes are related to weather conditions. Repeated rains with warm, humid, dull weather present favourable conditions for the development and survival of eggs and larvae on pastures, and given a supply of eggs from infested sheep (infestations may be very light) an outbreak is almost certain to occur.
WHY HAEMONCHUS IS AN IMPORTANT PARASITE.
This parasite is one of the most important internal parasites of sheep and produces disease in all sheep-raising countries.
it is important for the following reasons:-
(1). The female worms produce enormous numbers of eggs, about 5,000 per female per 24 hours, thereby heavily contaminating pastures in a relatively short time. Even lightly infested sheep will heavily contaminate pastures, e.g., a grown sheep harbouring 300 female worms of this species, while not showing symptoms, may disseminate 1,500.000 eggs every 24 hours.
(2). Haemonchosis is frequently of sudden onset, and deaths may also occur suddenly. Experimentally, sheep have died within three weeks of receiving a massive dose of infective larvae, having been actually bled to death by the developing worms. in the field, sudden outbreaks have been seen with deaths within a few weeks of contracting the infection. in such cases there are usually many immature worms present.
(3). There are no obvious symptoms unless sheep are handled or driven about the paddocks. Loss of condition is not seen in acute haemonchosis, and sheep in prime condition may die. Close examination of infested sheep will reveal anaemia, and driving them at a fast walking pace will show a lack of stamina that casual observation would not suggest.
(4). A high plane of nutrition is not very effective in preventing haemonchosis (it is much more helpful in trichostrongylosis and oesophagostomiasis). Outbreaks of haemonchosis commonly occur at times of the year when the plane of nutrition is high and even when it is rising.
(5). Haemonchosis frequently affects sheep of all ages in a flock. Trichostrongylosis on the other hand is seldom serious in sheep older than 18-24 months.
The great pathogenic significance of Haemonchosis should be more than offset by the high degree of efficiency of certain anthelmintic drugs against it in recent years. However, observations and experiments have shown that there are some very special circumstances attending the action of drugs in controlling the parasite. The following example will serve to illustrate one point: assume that a sheep harbours 2,000 Haemonchus and that treatment is 90 per cent. efficient. 200 worms will remain and of these about half will be females. These 100 females continue to produce 500,000 eggs every 24 hours. The disease may have been cured, but reinfestation is a persisting danger and under “outbreak” conditions sheep soon acquire new infestations.
ANIMALS AFFECTED.
Haemonchus affects sheep, cattle, and goats. it has been found in wild ruminants in other countries, but it does not occur in horses, marsupials or rabbits. Strains from cattle can infect sheep, and vice versa.
Haemonchosis in cattle is usually a disease of young stock, but in sheep, when outbreak conditions prevail, animals of all ages in a flock may become heavily infested. A higher proportion of young sheep will be infested than older sheep, and the latter will tend to recover more rapidly. in older sheep the “self-cure” phenomenon is more often manifest, but in aged sheep the disease is often serious.
SYMPTOMS AND DIAGNOSIS.
Diagnosis
Diagnosed through faecal egg counts & clinical examination, you may see us use an eye colour chart (the FAMACHA system) for grading anaemia in relation to H.contortus burden. The chart allows us to assess the degree of anaemia, and therefore H.contortus burden, by tracking changes in membrane colour. In more severe cases haemonchosis is diagnosed at post-mortem examination.
Control is through having a good parasite management system. Regular faecal egg count tests should be performed, especially through the warmer risk period and if treatment is indicated, a faecal egg count reduction test performed to check resistance status. H.contortus resistance is a particular problem, so treatment should be targeted and specific rather than blanket treatment across your entire flock.
Anaemia is the characteristic symptom of haemonchosis and is shown by pale skin, gums and conjunctival membrane. in severe cases oedema develops and “bottle jaw,” thickened lips and drooping ears may be seen. Anaemic sheep have no stamina and will only travel a short distance before lying down. There is usually no diarrhoea, but when haemonchosis coincides with a flush growth of pastures the faeces may be soft or even diarrhoeic. The parasite itself does not produce scouring. The intensity of “bottle jaw” varies from time to time, being most marked after sheep have had their heads down grazing and tending to disappear after they have been lying down. it is frequently not noticeable in the morning, but may be quite obvious in the afternoon of the same day.
The symptoms are almost diagnostic, particularly when seen during the warmer months of the year. Almost identical symptoms occur in chronic fluke disease, but this is usually seen in winter. The possibility of deficiencies of cobalt and copper should be kept in mind when anaemic sheep are under observation. Some of the poorer tableland country may be somewhat deficient in these trace elements. The finding of large numbers of H. contortus at autopsy will decide the cause of anaemia in most cases.
The only other vigorous, blood-sucking, internal parasite of sheep in Australia is the hookworm (Bunostomum), but the limited distribution and light infestations seen here indicate that it is not likely to be a common cause of anaemia. It occurs most commonly in the Upper Hunter Valley and is worth keeping in mind. Heavy infestations with immature Chabertia ovina or with the Ked Melophagus ovinus) may produce some degree of anaemia.
In severe infestations with H. contortus counts of 20,000 to 40,000 eggs per gramme of faeces are common. Counts of less than 4,000- 5,000 eggs per gramme are usually not of pathogenic significance, but sheep showing such counts are passing upwards of 2,400,000 eggs every 24 hours and are of considerable significance in relation to initiating or continuing outbreaks.
In making faecal examinations for the diagnosis of haemonchosis the pretence of immature worms must be considered, for sheep may die from the disease before the worms have reached the egg-producing stage. The females begin egg production about the 15th day after their ingestion as larvae, reaching maximum production after a month. The eggs of H. contortus are very similar to those of many other gastrointestinal parasites of sheep, and one should not reply on their appearance for exact diagnosis. A faecal culture should be made to obtain the characteristic larvae with medium length tails.
At post-mortem examination, if the sheep has been killed or has just died, the worms are readily seen wriggling vigorously in the contents of the fourth stomach, in their fresh state they are reddish and the females show the characteristic barber’s pole appearance, due to the twisting of the white, egg-filled uterine tubes round the red, blood-filled intestine. The male is smaller and is a uniform, brownish-red.
If a sheep has been dead for some time the worms are dark brown and may be partly disintegrated. Sometimes, in sheep which die of haemonchosis, many of the worms are found in the first few feet of the small intestine, usually being dark brown and showing early disintegration.
The only other common inhabitants of the abomasum are Ostertagia spp. and Trichostrongylus axei. The latter is very small and will not be seen unless scrapings from the mucosa are taken and examined in water in a glass dish. Ostertagia spp. are brown, about one-third the size of H. contortus, and are usually found in greatest numbers at the pyloric end of the abomasum. Immature H. contortus may at times be confused with Ostertagia spp., and it may be necessary to differentiate by microscopic examination.
CONTROL MEASURES.
General.
- contortusis the most vulnerable of all sheep parasites and most of the commonly used anthelmintic drugs are reasonably effective. There are, however, a number of special features rendering control difficult. The extremely high reproductive rate of the parasite is the chief of these. Others include the resistance of the immature worms to anthelmintics and variations in the efficiency of drenches containing copper sulphate.
It is essential in dealing with an outbreak to move sheen from contaminated pastures to areas which are free, or relatively free, from contamination.
TREATMENT.
The following drugs are commonly used against H. contortus:— Copper sulphate, copper sulphate-nicotine sulphate mixture, carbon tetrachloride, copper sulphate-arsenic mixture, arsenic, and numerous proprietary mixtures.
With the exceptions of carbon tetrachloride and phenothiazine, no drugs are efficient against H. contortus unless they are swallowed into the abomasum. Copper sulphate has the property of stimulating the oesophageal groove reflex and is swallowed into the abomasum in a high proportion of sheep. In experiments at the abattoirs and in the field, copper sulphate was swallowed into the abomnasum in 88 per cent. of sheep. In 12 per cent. of sheep, on the average, it was swallowed into the rumen or reticulum. On occasions there were as many as 30 per cent. of sheep in which this occurred. Drugs given with, or immediately following, copper sulphate were also swallowed into the abomasum by 88 per cent. of sheep.
When one uses a drench consisting of copper sulphate or mixtures of this drug with nicotine or arsenic, one must realise, therefore, that treatment will fail on the average in 12 per cent, of sheep. Formerly it was thought that if treatment was repeated within a few days the sheep which had “missed” on the first occasion would probably respond to the second treatment. Recently, however, a large amount of evidence has been assembled which shows that sheep which fail on one occasion are likely to fail on subsequent occasions. These sheep are likely to die from the effect of haemonchosis, or, should they survive, will continue to contaminate pastures with eggs, thereby prolonging the outbreak.
Copper sulphate is efficient against H. contortus in young sheep, but in adult sheep it is not efficient at the dose rates usually employed. Experiments and observations in the field have demonstrated this failure. It is necessary to double the dose of copper sulphate to ensure satisfactory efficiency in adult sheep. The dose usually recommended for adult sheep is 1 fl. oz. of a 4 per cent. solution, or 2 fl. oz. of a 2 per cent. solution, and it is necessary to use 2 fl. oz. of 4 per cent. solution, or 1 fl. oz. of an 8 per cent. solution. {Editor: it appears the first dose rate is for lambs and the second dose rate for adult sheep} The doses for young sheep should not be increased. It has been found that copper sulphate is very inefficient against immature H. contortus. Its use must, therefore, be repeated at short intervals in order to destroy worms as they mature. Copper sulphate is cheap and relatively “safe.”
Copper sulphate-nicotine sulphate mixture is very efficient against H. contortus in both young and grown sheep. It is more efficient than copper sulphate alone for killing immature worms, but is not highly efficient in this respect. It is expensive and if excessive doses are given toxic effects may be seen, particularly in poor sheep. In sheep suffering from a severe anaemia this mixture is apt to be toxic, particularly in hot weather. Should the mouth be injured during its administration severe abscess formation will occur. It is one of the few anthelmintics which are reasonably efficient against Trichostrongylus spp., and therefore can he used in the control of this parasite as well as against H. contortus.
Copper sulphate-arsenic mixture is very efficient against H. contortus in both young and grown sheep, and is equal to the copper sulphate-nicotine sulphate mixture against the immature forms. It is cheap and if dose rates are adhered to, is quite safe.
Arsenic alone is probably equal in efficiency to the copper sulphate-arsenic mixture, provided it is swallowed into the abomasum. Should it enter the rumen it is ineffective, and it has been shown experimentally to do this in an average of 50 per cent. of sheep.
Carbon tetrachloride is very efficient in both young and grown sheep. It is not efficient in killing immature worms, being intermediate in effect between copper sulphate alone and mixtures of copper sulphate with nicotine or arsenic. It is very readily administered and in the vast majority of instances is quite safe, but distressing mortalities occasionally follow its use. It is not as expensive as the copper sulphate-nicotine mixture. Its great merit is that it is efficient, irrespective of whether swallowed into the abomasum or the rumen.
Phenothiazine is highly efficient against H. contortus, killing both immature and mature worms. It is too expensive at present for general use against this parasite.
From these considerations it is evident that the choice of a drench is not a simple matter. One must consider soct, safety and efficiency—and in the case of nicotine sulphate and carbon tetrachloride availability may soon become an additional consideration.
When copper sulphate or its mixtures with nicotine or arsenic are used it is essential to use carbon tetrachloride as an alternating treatment, if not for the whole flock, then at least for those individuals which, judging by the persistence of symptoms, have not responded to treatment.
As copper sulphate is ineffective against immature worms, it is unwise to use it during outbreak conditions unless one is prepared to repeat treatments about every seven days. This applies also to carbon tetrachloride. Copper sulphate-nicotine sulphate is expensive. Copper sulphate-arsenic mixture is cheap and effective and appears to be a logical choice for general use against H. contortus, provided carbon tetrachloride is used to cure cases which have failed to respond to it.
Treatment and control :After confirmation proper treatment with suitable drugs and managemental care are provided to the entire flock. Therapeutic management included combined anthelmintic treatment ivermectin (Neomec® , Intas Animal Health, India) and albendazole (Albomar® , Virbac India). Ivermectin was administered @ 1 ml /50 kg body weight S/C. Albendazole was administered 5 mg/kg bodyweight orally. Livotas® (Intas Animal Health, India) @ 5ml/ animal orally twice daily is administered as liver support. In addition to the proper therapeutic management, movement of the animals are restricted and fed them with concentrates along with green tree leaves and grasses. Stall feeding practice and grazing management reduces the exposure to reinfection with worms and the animals regained their health condition gradually. The effect of changes are made in the dietary provisions may be supported by the findings of Atiba et al., (2020) which suggests that Protein supplementation seems to improve host resilience to deal with detrimental effects of the infection and hence improves production and reproductive performances of animal. Dietary supplementation of Condensed Tannins improves the Nitrogen (N) retention, and inhibited the different developmental stages of Haemonchus contortus in experimental sheep. (Pathak et al., 2013).
In conclusion the present communication it is observed that during the rainy season the morbidity rate of H. contotus infection in goat is found to be considerably higher, this might have attributed to high pasture larval burden in the grazing areas nearby the farm. Mortality is also recorded but implementation of proper therapeutic (combined anthelmintics) as well as managemental practices prevented the further fatalities among the flock. In the present communication some animal recovered suggesting that anthelminitic resistance is not developed in the infected animal. It can be concluded that during high rainy seasons the animal should be properly check for any parasitic infestation and proper deworming should be followed at least four month interval. Stall feeding and restricted movement can also reduced the occurrence of haemonchosis in goat.
Compiled & Shared by- Team, LITD (Livestock Institute of Training & Development)
Image-Courtesy-Google
Reference-On Request.
