The "Big Five"
In May 2015, I spent two weeks in South Africa. It was the trip of a lifetime. I had wanted to go on a African safari since I was a little girl, when two of my favorite TV shows were Tarzan and Daktari. As an Extension Sheep and Goat Specialist, South Africa had also been a place I had always wanted to visit. Most of what I teach about internal parasite control (in small ruminants) was developed in South Africa. South Africa is one of the world's leaders in sheep and goat production. Many important breeds have been developed there, including the Dorper and Boer.
During my trip to South Africa, the words "Big Five" meant two things. To big game hunters, the Big Five are the five most difficult animals to hunt: lion, leopard, rhinosaurus, buffalo,and elephant. Safari tour operators have adopted the same phrase for marketing purposes. Every tourist, including me, wants to see the Big Five.
South African veterinarian Dr. Gareth Bath used the words Big Five to divide parasite control strategies into five BIG categories: 1) animals (host); 2) worms; 3) pastures; 4) monitoring; and 5) treatment.
What Works With Worms
My primary reason for visiting South Africa was to participate in W4: What Works With Worms, an International Congress on Sustainable Parasite Control. The Congress was organized by the South African Veterinary Association, the veterinary faculty of the University of Pretoria, and the American Consortium for Small Ruminant Parasite Control (ACSRPC), of which I am a member. I maintain the consortium's web site at www.acsrpc.org or www.wormx.info.
South African veterinarians are among the many international collaborators in our consortium; so we decided to hold our annual spring meeting in South Africa (Pretoria). I gave two presentations at the Congress, which was attended moslty by farmers and veterinarians: 1) Getting the message across to farmers; and 2) The role of pasture management in controlling intestinal parasites.
Dr. Gareth Bath from the University of Pretoria gave the final presentation at the Congress. He summarized the two-day event in a presentation entitled "(Putting it all together) The Big Five: a South African Perspective on Sustainable Holistic Internal Parasite Management in Sheep and Goats."
The Big Five of Parasite Control
# 1 Animals
Professor Bath coined the phrase, "Stop Selecting Sissy Sheep," to emphasize the importance of host resistance; it's corallary is "Sissy Sheep Seldom Survive." According to Dr. Bath, too much emphasis has been placed on anthelmintic resistance as opposed to sheep resistance. Sheep and goats can be selected and bred for increased resistance and resilience to internal parasites. There are examples of this being done with sheep.
Primary emphasis should be placed on ram selection. Rams with low fecal egg counts should be selected for breeding. While the selection standards for ewes and does cannot be as strict as those for males, it is still imporant to select ewes that are more resistant to worms. However, instead of selecting the top ewes, the goal is to cull the bottom end. Targeted selective treatment using the Five Point Check© can be used to achieve this goal.
Good nutrition, especially protein and trace minerals, is essential to supporting immunity. Animals cannot express their genetic potential for parasite resistance and resilience if they are not adequately fed. The importance of dietary protein has been well-established. Less is known about the importance of trace minerals.
In order for an animal to develop immunity to parasites, there needs to be adequate exposure (challenge). The goal should not be to eradicate parasites, but rather to establish a balance between the host and parasites. At the same time, exposure cannot be so great that it overcomes the natural ability of the animal to resist worms.
If animals are suffering from other diseases, they may not be able to express their genetic potential for parasite resistance and resilience. It is important to control other disease factors.
It is important not to introduce resistant worms to the farm. Newly acquired animals should be properly quarantined and dewormed to prevent the introduction of resistant worms.
# 2 Worms
Parasite risk is a numbers game: fecal egg counts; number of larvae that hatch, mature, and survive; number of infective larvae that are consumed; number of larvae that mature into adults; and number of eggs laid. Other numbers of importance include livestock numbers, numbers of days on pasture, days of pasture rest, and prolificacy in egg laying.
Since it can take a week to several months (depending upon the climate) for eggs to hatch and the larvae to become infective, the shorter the period of grazing, the less chance there is of a severe build-up of infective larvae. Short duration, high pressure grazing not only improves pasture utilization, but brings parasite control benefits.
If length of stay cannot be reduced, then the number of animals grazing a pasture should be reduced. Pasture contamination can be lowered by reducing the number of animals that graze a unit of land. The period of pasture rest is crucial to reducing the build-up of infective worm larvae. The period of rest required varies from one month to several months, depending upon climate.
Another way to remove infective larvae from a pasture is to graze the pasture with non-susceptible species, such as cattle and horses. "Hot spots" increase the risk of severe parasitism and should be avoided. Examples of hot spots include grassed pens, marshy areas, and leaky water troughs. Sheep and goats are attracted to these better-watered and fertilized grazing spots.
Pasture fertilization improves pasture growth, but indirectly protects larave from dessication. Fertilization also improves pasture palatability which encourages intake, resulting in more infective larvae being ingested.
# 3 Pasture
Since pasture is the vector for transmission, it is essential that pasture factors be considered when developing a parasite control program. The risk of infection is dependent upon the height of the pasture. It is well known that the infectivity of pasture decreases in a logarithmic fashion as the height of the pasture increases. Short-cropped pastures carry an increased risk of pasture infectivity.
The type (species) of pasture affects the risk of parasitism. Certain pasture species are more prone to spreading parasite infection. Sericea lespedeza has been shown to contribute to parasite control. The slope of a pasture affects run-off and therefore larval survival. Pastures with good drainage carry a lower risk of severe parasite infection as compared to poorly-drained paddocks. The direction that a pasture faces (aspect) also affects risk. Slopes that get less direct sun are cooler and will retain their moisture longer. Extra water on pasture (e.g. irrigation) can increase risk. Soil type may have an effect on risk. Heavy, clay soils retain moisture more than light, sandy soils.
# 4 Monitoring
Though less useful for monitoring the parasite burden for indivdiual sheep, fecal egg counts can be used to monitor the infection rate on pasture. Collecting pool samples every month is a good plan. Before and after fecal egg counts can be used to efficacy of anthelmintics. Individual animals should be tested. Pooled samples can be used to test for anthelmintic resistance, if the samples are collected from the same animals.
The Five Point Check© and other criteria such as weight gain and milk production can be used to assess the effect of parasities on individual animals. The FAMACHA© system is the most extensively researched component of TST.
The weather (rain, humidity, and temperature) can be monitored to predict conditions which are favorable to larvae development. Unfortunately, there is no scientific model which indicates the level of risk. Grazing conditions also affect risk of parasitism.
# 5 Treatment
Drugs are an essential component of TST. However, they must be used effectively and frugally to ensure their continued usefulness. Most anthelmintic resistance can be traced back to frequent and inappropiate use of drugs.
Targeted Selective Treatment (TST) and Targeted Treatment (TT) should be implemented on all farms. The FAMACHA© system is the most widely used component of TST. The Five Point Check© is a simplified extension of the FAMACHA© system for use against other major parasites. It is gaining acceptance in the sheep and goat industry.
It is important to follow drug labels. Drug dosage should be based on weight. Most producers do not accurately guess the weight of their animals. Underdosing accelerates the development of resistant worms. If an automatic drench gun is being used, it should be set for the heaviest animals in the group. The gun should be checked for accuracy and repeatability.The most vulnerable members of the flock/herd should receive special attention, e.g. lambs/kids and lactating or heavy pregnant females.
After the Congress was over, we went on a post-conference tour, organized by our South African hosts. The tour included several farms, a few historical sites, and four days at Kruger National Park.
The first farm we visited raised both sheep and cattle. They had about 800 Merino ewes. Their production emphasis was obviously wool, which they sold on a clean basis. Only about 20 percent of their ewes typically give birth to twins. A portion of the flock is fitted with collars, so that the farmers receive a text message when the flock is disburbed. Theft of livestock is a major problem in South Africa.
We visited the farm where the FAMACHA© system was developed. Sadly, the farm was redistributed and and is no longer being actively farmed. One man was growing vegetables on the farm, but when he sold them to the government, his payment would be delayed by more than six months. There was a nice-looking herd of (beef) cattle on the farm, but we didn't learn anything about them. The dairy facilities on the farm were no longer being used. They were in disrepair. The road into the farm was barely passable.
We visited another farm where the farmer had stopped raising sheep, due to heavy losses from theft. It had also become less profitable to buy and feed lambs. He was currently growing out heifers. Those that don't conceive, he feeds out for market. Though he didn't have sheep on his farm, the farmer spoke favorably about sericea lespedeza. Our consortium has done considerable work with sericea lespedeza, primarily for its activity against internal parasites. At one of our consortium meetings, another South African farmer spoke about his experiences with sericea lezpedeza.
The rhino is one of the Big Five wildlife.
Making friends with a cheetah (image by Bob Storey)
The Big Five: Monitoring (FAMACHA© scoring)
We visited a farm supply store. It offered an amazing supply of pharmaceuticals and anthelmintics. In South Africa, there are eleven different anthelmintic classes, compared to only three in the US. Many of them are drug combinations. In fact, I bought a container of First Drench, a combination dewormer that is unavailable in the US. Zolvix® is by prescription-only in South Africa, so I wasn't able to get any.
I arrived several days before the Congress. During those days, I visited sheep farms with final year vet students from the University of Pretoria. Both of the farms we visited were Dorper stud farms. On the first farm, the students vasectomized some rams. A couple of the rams were South African Meat Merino (SAMM). The farmer used artificial insemination in his own flock and also did AI for other farms. The sheep and lambs looked good.
On the other farm, the students worked through a flock of Dorper ewes and lambs. They docked the lambs using a burdizzo. I've never been a fan of using the burdizzo for tail docking, but by holding the burdizzo in place after clamping, there was minimal blood loss. Usually the farmer banded his lambs. These lambs were too big for banding. The students scored all of the sheep for FAMACHA©, pigment, age, and body condition. Only a few sheep required special treatment. Most of the ewes and lambs looked very good.
Kruger National Park
Kruger National Park is one of the largest game reserves in Africa. It covers an area of 7,524 square miles and is located in the northeastern part of South Africa. The land was first protected by the government in 1898 and Kruger became South Africa's first national park in 1926. Some controversary surrounded the establishment of the park, as lands were taken from indigenous peoples. According to a museum at the park, the park was perceived differently by white and black South Africans.
While visiting the park, we went on several game drives, including a night drive and early morning drive. Both drives resulted in prolific sightings of wildlife. When it was dark, we used spotlights to locate animals by their eyes. On the night drive, the first animal we saw was a leopard, the most illusive of the Big Five. Unfortunately, he was on the "wrong" side of the vehicle and I wasn't able to get a good picture of him. We also saw lions on the night drive: several lionnesses and a young male. They were resting peacefully.
On the morning drive, our first sighting was a spotted hyena. He was walking alongside the road, without a care in the world. He was on my side of the vehicle, but I was holding the spotlight, so my picture of him is a big blur. We saw lions again, more females and a young male. I never tired of these King of the Beasts. We were treated to a beautiful sunrise on the morning drive.
The morning after we arrived in Kruger, we listened to a lecture at the Veterinary Services building. We learned about the poaching problem with rhinos. Sadly, rhino horns are very valuable, in high demand in the Far East, mostly Vietnam. Both poaching and anti-poaching efforts have become very sophisticated. The park uses drones to monitor poaching.
Legalization of the trade (in rhino horns) is being explored as a possibility to combat poaching. If trade were made legal, rhinos could be raised (on farms) and their horns could be humanely harvested (horns grow back in time). It is uncertain as to whether this strategy could be successful. Dehorning rhinos is another possible option, but not without drawbacks. A biotech start-up hopes its fake rhino horns will curb poaching.
Sadly, a few hours later we saw a dead rhino. It was too far away to see if it still had its horns. We later learned that it died from natural causes. During our stay in Kruger, we were rewarded with several rhino sitings, some very close. In fact, one siting, along the rhino trail at our camp, broke up our consortium meeting. The first distraction had been a baboon. By the time I took his picture, all I captured was his ass. It is impossible to keep monkeys and baboons out of the camps.
Rhinos are spectacular animals. They move slowly and graze very close to the soil surface. They reminded me of dinosaurs. Rhinos may be white or black in color. We saw the white ones. The black rhinos are seldom seen, as there are fewer of them in Kruger. According to the guidebook, white rhino calves walk in front of their mothers, wheras black rhino calves follow behind their mothers. Interesting!
One of the animals I most looked forward to seeing was the hippopotamus (hippo). Fortunately, we saw some, but they were far away. Mostly they were out of the water, sunning themselves. I had always heard that hippos kill more people than any of the other African wildlife. It's hard to imagine, but they say that they are very fast.
We saw giraffes on several ocassions. They were never very close to our vehicles. Elephants were a fairly frequent sighting. We were told not to shine the spotlight in their eyes or make a lot of noise. If you kept quiet, you could hear them grazing or rather knocking down trees. Elephant poop was plentiful in the park. They do not digest their food very efficiently. We saw a couple of baby elephants. It was hard to get clear pictures of the elephants, as they were often blocked by tree branches. On several ocassions, we saw elephent "herds" from a distance.
The most numerous mammal in Kruger National Park is the impala, dubbed "the McDonald's of the Bush." It was the rutting season. We didn't see any babies. The impala is a very elegant looking antelope, similar to a white tailed deer. We saw numerous other antelope-type species, including water buck, wildebeast, kudu, and common duiker. During our drives, we munched on jerkie made from some of the aforementioned species. When a restaurant offered venison, it could be any of these antelope-type species.
On our last day in the park, we saw a herd of zebras, near a watering hole. Zebra stripes come in different patterns, unique to each individual. Genetically, zebras are black with white stripes. While (domestic) horses aren't my favorite animal, I was absolutely enthralled by the zebras. They seem so fat and jolly. In fact, one of the tour guides told us that it is rare for a zebra to be fat.
We were greeted by a herd of (cape) buffalo, another of the Big Five, on our last game drive. One bull was covered in mud. We saw a couple of calves. We were told that the buffalo is one of the last animals you would want to encounter in the bush, as they are very aggressive and dangerous. I have to admit they were the animal that seemed to show the most interest in us.
Some of the other wildlife we saw included (vervet) monkeys, dwarf mongoose, ostriches, crocodiles, ducks, turtles, scrub hares, and warthogs. I was not able to get any close-up shots of the warthogs and none had any babies in tow. Two scrub hares ran in front of our truck for at least a mile, during our morning game drive. There were also many beautiful birds. The African bush is a bird watcher's paradise. My favorite fauna was the sausage tree.
There was an interesting cemetary at the park. Little Heroes' Acre contained headstones of dogs killed in the line of duty at Kruger National Park. On numerous ocassions, dogs saved the lives of game rangers. I went around the cemetary and read about all the dogs. There was one named Jack, the name of my first dog.
We were told that our group saw more wildlife in a few days than many people see in a lifetime. We saw the Big Five and lots more. Kruger was a fantastic experience!
This article was written in 2015 by Susan Schoenian.