AGRICULTURE NEWS - Rain is always welcome in our semi-arid country. There should be preparation for a boom in parasite populations and diseases like Rift valley fever. 

We need to take the necessary precautions as this season has already proven to be wetter, warmer, and longer. 

Parasites and parasite diseases are benefiting from the increased rainfall in Southern Africa. 

Dr Peter Oberem, Managing Director of Afrivet warns: “This means that we must be more vigilant; early detection and intervention is critical in ensuring the success of treatments. Vaccinate where possible to prevent outbreaks and to reduce their impact. Diseases and parasite that come to mind are Rift valley fever, blue tongue, horse sickness, redwater (babesiosis), heartwater, gall sickness (anaplasmosis), ephemeral fever and lumpy skin disease, as well as ticks and worms such as wire worm in sheep”

Some parasites are vectors of disease and cause loss of production, for example flies.  House flies and biting flies  irritate animals, and may lead to decreased production. They can also transmit diseases e.g. biting flies transmit lumpy skin disease.

Ticks are   external parasites, which are vectors of disease, but also cause severe damage due to bites, toxicoses. Single-host ticks, e.g. blue ticks: their entire lifecycle (larvae to adult) occurs on one host.  Multi-host ticks, e.g. bont tick and bont-legged tick: each lifecycle stage is spent on a different host animal. The larvae, nymphs and adults take a blood meal, fall off, climb on the next host, and repeat the cycle.

Both types of tick populations can increase after abundant rainfall, but the single-host tick will be more prevalent as it only needs a single host to reproduce.

Farmers must inspect their animals every day to spot ticks early on, to determine the efficacy of dips and to prevent disease development.

Blue tick larvae, for example, transmit red water, the symptoms of which should become evident after about two weeks. An engorged blue tick, has been around its host for two weeks, and should be taken as a red-water warning. Single-host ticks are found on animals’ necks and shoulders, while multi-host ticks usually keep to less obvious parts of the body.

In addition to dips, sprays, and pour-on remedies and spot treatments can be used to control ticks. When animals are covered in ticks, it could indicate a weakened immune system and nutritional deficiencies. 

Helminths, generally referred to as worms, include roundworms, tapeworms, and flukes.

• Wireworm is one of the most common worms in the summer rainfall areas and thrives in wet conditions. Regular deworming can control this parasite, but the downside is that anthelminthic resistance is prevalent in this species. Faecal egg counts can help determine if there is anthelmintic resistance on your farm. The use of the Wirevax vaccine reduces the number of treatments which need to be given.
• Liver fluke and conical fluke infestations   increase during wet conditions because these parasites need water to complete their life cycles.

Mosquito populations increase during rainy seasons and certain species which prefer livestock can transmit   Rift Valley fever (RVF), a virus that can be deadly to animals and humans alike. South Africa has suffered three major RFV outbreaks since 1951, with the latest being in 2011.

Both types of tick populations can increase after abundant rainfall, but the single-host tick will be more prevalent as it only needs a single host to reproduce.

Even though history suggests that the next major outbreak should only occur in about 2040, smaller sporadic outbreaks remain a real possibility. RVF symptoms in sheep, cattle and goats include abortion storms (80% to 100 % of pregnant animals can abort) and sudden death in young animals. The mortality rate in adult animals is between 10% and 20%, but many will endure symptoms such as drooling, a runny nose, fatigue, diarrhoea, and fever.

Humans can contract the disease when they handle blood or organs from infected animals. Symptoms can range from mild cold or flu symptoms to serious bleeding disorders and even death. As a precaution Meat should never be consumed from dead or dying animals. 

Fly control remedies such as Deltapor 5 and IconCS   decrease   the mosquito numbers   around but must be applied regularly to prevent mosquito bites, so the most effective prevention strategy is vaccination combined with vector control.

Two registered vaccines are available in South Africa, produced by Onderstepoort Biological Products (OBP):

• The live vaccines Smithburn and Clone 13 are highly effective and provide long-lasting immunity; they should be applied annually to ensure continued protection.
• The inactivated vaccine: which should be the appropriate option for pregnant animals, may be inadequate for use in pregnant animals, as it  requires 3 vaccinations for solid immunity to develop.

How to be responsible regarding RVF:

• Vaccinate! Don’t wait for the outbreak, build the immunity of your animals before; Non-vaccinated animals are fully susceptible.
• Practice vector control by putting a mosquito and management system in place.
• Report any suspected cases in animals and humans to your local state veterinarian.

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