Parasites pose a significant challenge to the health and productivity of non-ruminant animals in Kenya's agricultural sector. Effective management of these parasites is crucial for extension professionals who support farmers in improving livestock performance and ensuring food security. This chapter explores the fundamental concepts of non-ruminant parasites, focusing on their definitions and classifications, which form the basis for understanding control strategies tailored to the Kenyan agricultural context.

3.1 Non-ruminant parasites

Non-ruminant animals such as pigs, poultry, rabbits, and equines are susceptible to various parasites that can reduce growth rates, cause diseases, and increase mortality. Understanding the nature of these parasites is essential for effective intervention and extension advisory services. This section introduces the terminology and diverse types of parasites affecting non-ruminants, highlighting their relevance to agricultural productivity in Kenya.

3.1.1 Definition of terms

Precise terminology is essential in parasitology to ensure clear communication among extension officers, farmers, and veterinary professionals. This subtopic clarifies key terms related to non-ruminant parasites, laying a foundation for subsequent discussions on their management.

Parasite

A parasite is an organism that lives on or inside another living organism, called the host, deriving nutrients at the host's expense. Parasites can cause harm ranging from mild discomfort to severe disease, impacting the health and productivity of non-ruminant animals such as pigs and poultry in Kenya. For instance, the pig parasite Ascaris suum causes intestinal damage and poor weight gain in commercial pig farms.

Host

The host is the organism that harbours the parasite, providing it with shelter and nutrients. In non-ruminant livestock, the host can be animals like chickens, rabbits, or horses. Hosts may suffer from reduced productivity or illness due to parasitic infestation, which can result in economic losses for farmers, for example through poor growth in a pig unit or fewer eggs from a layer flock.

Hosts are described according to their role in the parasite's life cycle:

• Definitive host: the host in which the parasite reaches adulthood and reproduces. A pig is the definitive host of Ascaris suum.
• Intermediate host: a host in which the parasite passes a larval or developmental stage. Earthworms and insects such as beetles and grasshoppers can act as intermediate hosts for some poultry tapeworms.
• Paratenic (carrier) host: a host in which the parasite survives without developing further, but from which it can infect the next host. Earthworms carrying Heterakis eggs are an example.

Infestation and Infection

Infestation generally refers to the presence of external parasites such as lice and mites on the animal's body surface, causing irritation and skin damage. Conversely, infection pertains to internal parasites like worms inhabiting the gastrointestinal tract or organs. Differentiating between infestation and infection is critical for selecting appropriate treatment methods.

Endoparasites and Ectoparasites

Endoparasites live inside the host's body, often in the digestive system or tissues, while ectoparasites live on the host's surface. For example, poultry can suffer endoparasitic infection from coccidia, leading to coccidiosis, while ectoparasites like the fowl mite cause external irritation.

Parasitism

Parasitism is a biological relationship where one organism benefits (parasite) at the expense of another (host), often causing harm but not immediate death. This interaction affects animal welfare and productivity, making parasitism a central concern in livestock management in Kenya's farming systems.

Vector

A vector is an organism, usually an insect or tick, that carries a disease-causing agent from one animal to another. Vectors may carry the agent on their mouthparts or body (mechanical transmission) or the agent may develop inside them (biological transmission). Biting flies that move between horses in a stable can spread blood parasites in this way.

Obligate and facultative parasites

An obligate parasite cannot complete its life cycle without a host, for example the poultry roundworm Ascaridia galli. Facultative parasites are organisms that can live freely in the environment but may become parasitic under certain conditions. Examples include some fly larvae that infest wounds, decaying tissue or soiled skin, such as blowfly strike in rabbits. In Kenya's smallholder farms, poor hygiene can lead to facultative parasitic infestations, worsening animal health.

3.1.2 Types of non-ruminant parasites

Non-ruminant animals are affected by a wide array of parasites that vary in biology, mode of transmission, and impact on the host. A thorough understanding of these types enables extension professionals to recommend targeted control measures. Parasites are grouped by where they live: internal parasites inside the body and external parasites on the body surface.

3.1.2.1 Internal parasites

Internal parasites (endoparasites) live in the digestive tract, liver, lungs, blood or other tissues of the host. They feed on digesta, tissue or blood, damage organs and compete with the animal for nutrients, so infected animals grow slowly, convert feed poorly and may die in heavy infections. Most are spread when the animal swallows eggs or oocysts passed in faeces by other animals, which is why crowded, dirty housing favours them.

Helminths (worm parasites):

Helminths are multicellular worms that infest internal organs, primarily the gastrointestinal tract. Common helminths in non-ruminants include roundworms, tapeworms, and flukes. In pigs, Ascaris suum leads to reduced feed conversion efficiency, while in poultry, nematodes like Heterakis gallinarum can transmit diseases such as histomoniasis (blackhead). Common examples by host are:

• Large roundworm of pigs (Ascaris suum): adult worms live in the small intestine, while migrating larvae damage the liver and lungs. Affected pigs cough, grow slowly and may show white scarred patches on the liver at slaughter.
• Nodular worm and whipworm of pigs (Oesophagostomum and Trichuris suis): these live in the large intestine and cause scouring and weight loss, especially in pigs kept on dirty, damp floors.
• Poultry roundworms (Ascaridia galli and Heterakis gallinarum): Ascaridia lives in the small intestine and causes weight loss and poor egg production, while Heterakis lives in the caeca and carries the organism causing blackhead.
• Poultry tapeworms (Raillietina species): flat, segmented worms in the intestine that need an intermediate host such as a beetle or ant, so birds on free range are more exposed than caged birds.
• Equine strongyles and ascarids: large and small strongyles in the large intestine cause colic and poor condition, while Parascaris equorum is most serious in foals, where heavy burdens may block the intestine.
• Pinworms and bots: Oxyuris equi in horses causes intense itching around the tail base, and Passalurus ambiguus occurs in the rabbit caecum. Bot fly larvae (Gasterophilus) attach to the stomach lining of equines.
• Flukes: liver and other flukes are less important in non-ruminants than in cattle, sheep and goats, but they can occur where animals graze or drink in wet, snail-infested areas.

Protozoa:

Protozoan parasites are single-celled organisms causing diseases such as coccidiosis in poultry and rabbits. These parasites multiply rapidly within the host, leading to symptoms like diarrhoea, weight loss, and mortality. In intensive poultry farming, protozoan outbreaks can cause significant production setbacks if not controlled promptly. Important protozoa include:

• Poultry coccidia (Eimeria species): multiply in the gut lining and cause bloody or watery droppings, ruffled birds and deaths, particularly in chicks kept on wet litter.
• Rabbit coccidia (Eimeria species): intestinal forms cause diarrhoea and wasting in weaners, while Eimeria stiedae damages the bile ducts and liver.
• Pig coccidia (Isospora suis): causes yellowish, pasty scour in piglets in the first weeks of life, especially in dirty farrowing pens.
• Balantidium coli: a ciliate living in the pig large intestine, usually harmless but able to cause dysentery when the gut is already damaged.
• Histomonas meleagridis: a protozoan carried inside Heterakis eggs that causes blackhead in poultry, damaging the caeca and liver.
• Trypanosomes: blood protozoa that cause trypanosomiasis in equines, spread by tsetse and other biting flies, leading to fever, anaemia, weakness and loss of condition.

3.1.2.2 External parasites

External parasites (ectoparasites) live on the skin, hair or feathers of the host, or in the skin itself. They cause irritation, blood loss, skin damage and secondary infections, and some also carry disease-causing organisms. They spread by direct contact between animals, through shared housing, bedding and equipment, or from the surroundings, so a single infested animal can quickly contaminate a pen, a poultry house or a rabbit hutch.

Ectoparasites live on the animal's skin or feathers, causing irritation, blood loss, and secondary infections. Common ectoparasites affecting non-ruminants include mites, lice, fleas, and ticks. For example, fowl mites reduce egg production and cause anaemia in layer hens, while ticks on equines can transmit debilitating diseases. The main groups are:

• Mites: tiny eight-legged parasites. Red mites (Dermanyssus gallinae) hide in cracks of poultry houses by day and feed on roosting birds at night. Scaly leg mites (Knemidocoptes mutans) burrow under leg scales. Sarcoptic mange mites (Sarcoptes scabiei) burrow into pig skin and cause intense itching and crusting, while ear mites (Psoroptes cuniculi) cause brown crusts inside rabbit ears.
• Lice: wingless insects that spend their whole life on the host. Chewing lice of poultry feed on feathers and skin scales, while the pig louse (Haematopinus suis) and horse lice suck blood and cause scratching, rough coats and poor growth.
• Fleas: small jumping insects that feed on blood. The sticktight flea (Echidnophaga gallinacea) attaches in clusters on the head and wattles of poultry, and fleas also infest rabbits and pigs kept in dusty, unclean housing.
• Ticks: blood-feeding arachnids. The fowl tick (Argas persicus) hides in poultry house crevices and feeds at night, causing anaemia and drops in egg production, while ticks on horses and donkeys damage the skin and may transmit disease.
• Biting and nuisance flies: stable flies, horse flies and midges bite equines, pigs and rabbits, causing restlessness, reduced feed intake and skin lesions.

Arthropod vectors:

Certain external parasites act as vectors transmitting pathogens between hosts. Ticks and flies are prominent arthropod vectors in non-ruminant systems. The stable fly (Stomoxys calcitrans) commonly infests livestock farms, causing stress and transmitting diseases such as trypanosomiasis in equines. Controlling these vectors therefore protects animals from both the direct damage of the parasite and the diseases it carries.

Chapter Summary

This chapter explored the concept of non-ruminant parasites by first defining key terms and distinguishing between internal and external parasites that affect non-ruminant animals. It detailed the common signs and symptoms of parasitic infestation such as loss of appetite, emaciation, staring coat, and dullness, which help in early detection. Various parasite control measures were examined, including deworming, spraying, dipping, dusting, vaccination, and fumigation, highlighting their roles in effective parasite management. The importance of preparing accurate parasite control records was emphasized to monitor treatment schedules and outcomes. Proper management of parasite control waste was also discussed to prevent environmental contamination and health risks. Practical skills were addressed through the identification of external parasites and the implementation of diverse control methods. Finally, the chapter covered the procedures for handling and disposing of parasite control waste safely to maintain hygiene and biosecurity in animal management.