Livestock Lament: The Myiasis Misadventures

 Understanding the Nightmare of Myiasis

Ah, the great outdoors—where pets and livestock frolic in the sun, enjoying the natural world. Yet, lurking in those picturesque meadows and farms is a tiny menace with a big appetite: the parasitic fly. Welcome to the wiggly world of myiasis, where flies lay eggs in the unlikeliest of places and maggots make themselves at home in our beloved animals. Grab your magnifying glass because we're diving into the bizarre, the grotesque, and the utterly fascinating realm of critters that turn pets and livestock into their personal buffets. Prepare to be grossed out and enlightened in equal measure.

 What is Myiasis/Flystrike?

Myiasis is an infestation of organs and tissues of host animals by dipterous fly larvae known as maggots. 

It affects both pets and livestock. It's a distressing issue that can lead to severe discomfort and health complications if left untreated. Myiasis leads to infection and, in severe cases, significant tissue damage. Various types of flies can cause myiasis, including blowflies, botflies, and screwworms. Each type has a different method of infestation, but the end result is the same: a painful and potentially dangerous condition for the affected animal. In this blog post, we will explore myiasis, how it affects different animals, the signs to look for, and the best ways to prevent and treat this condition.

Examples of myiasis causing flies

1. Nasal bots(Oestrus spp): Affects both sheep and goats.Parasites are found in the air passage (Nasal sinuses) of hosts, yellowish-white in colour. Laid by adult female grey flies that squirt a jet of liquid containing larvae at the nostrils of the host during flight. Larva feed on mucus.
2. Warble flies (Hypoderma spp): Affects cattle, equines (horses, donkeys), sheep and rearly man. The parasite is barrel-shaped, with most of its segment bearing spines, it's dirty-white in colour when newly emerged from the host. Adult flies have an abdomen covered with yellow-orange hairs with a broad band of black hairs around the middle. Parasites feed on the tissue of the host.
3. Bot flies(Gasterophilus spp): Affects mostly Equines. Parasites Migrate from where they're laid on the host into the body, where they wander in their preferred tissues, here it develop and are passed out in faeces to pupate in the soil.
4. Flesh flies(Sarcophaga spp): Larva are primarily scavengers found in decaying carcasses, rotting food, human and animal excreta and sometimes in wounds. they are typically maggot-shaped with spicules on the body. Adults are large, hairy non-metallic flies, greyish in colour.
5. Chrysomya: Infest all warm-blooded animals and not carrion.
6. Sheep blowflies(Lucilia): Affects sheep, and other domestic and wild animals, including humans. Adult flies are metallic-green coloured flies.
7. Phormia and Protophormia spp: Usually found in carrion and sheep. Adults are metallic blue-black in colour
8. Cordylobia spp: Infest rodents, dogs, and other domestic and wild animals including humans.

Why Myiasis Affects Pets and Livestock

• Preferred host e.g Nasal bots(Oestrus spp) which infests sheep and goats
• Soiled hair coat/wool or matted hair coat with faecal matter
• Open wounds
• unsanitary  living conditions

Signs of Myiasis

• Visible maggots on the skin or in wounds
• Nasal discharge, sneezing and rubbing of noses on fixed objects in Nasal bots infestation.
• Foul-smelling discharge due to larvae infestation.
• Restlessness, irritation or behavioural changes due to discomfort
• Swelling (nodule-like) or redness around an affected area
• Lethargy or a decrease in appetite
• In severe cases, systemic illness and/or death

What Myiasis causes in pets and Livestock

1. False gid: When a larva (Nasal bot) dies in the sinuses, there may be secondary bacteria invasion and cerebral involvement resulting in unthriftiness, circling and in-coordination.
2. Interrupted feeding: Animals (particularly sheep) on noticing the adult bot flies will panic, stamp their feet, bunch together and press their nostrils into each other fleeces and against the ground.
3. Panic/gad: Attempts by adults to lay eggs on the host act as a great source of annoyance to the host. This may lead to a stampede and injuries when animals attempt to run away from flies.
4. Partial paralysis/Paraplegia: This occurs when the Hypodermia bovis larva dies in the spinal cord with the release of proteolysis.
5. Oesophageal stricture/constriction: This occurs when the Hypodermia lineatum Larva dies in the submucosa of the oesophagus resulting in bloat and faulty regurgitation.
6. Analphylaxis: Hypersensitive reaction when larvae die in sensitized animals.
7. Cavernous lesions on skin: This occurs due to progressive liquefaction, tissue necrosis and haemorrhage caused by larvae embedded in tissue.
8. Cutaeneous margins: Migration Tracks on skin/tissue of parasitic fly larvae resulting in rejection of animal by-products (i.e) Meat at meat inspection and decreases in the value of its hide and skin.

Preventing Myiasis

1. Regular Grooming: Keep pets and livestock clean and well-groomed. Regular brushing helps to remove debris and check for signs of infestation.
2. Wound Care: Promptly clean and treat any wounds. Use appropriate antiseptics and cover them if necessary to prevent flies from laying eggs.
3. Environmental Management: Maintain clean living areas for animals. Remove waste and ensure bedding is dry and clean.
4. Fly Control: Implement fly control measures such as insect repellents, fly traps, and screens in animal housing areas.
5. Shearing and Crutching: For sheep, regular shearing and crutching (removal of wool around the tail and breech area) can significantly reduce the risk of flystrike.

Treating Myiasis

1. Removal of Maggots: Carefully remove visible maggots using tweezers or similar tools. It’s essential to be thorough to prevent re-infestation.
2. Cleaning the Wound: Clean the affected area with antiseptic solutions to prevent secondary infections.
3. Medication: Your veterinarian may prescribe antibiotics to combat infection and anti-parasitic medications to kill any remaining larvae.
4. Supportive Care: Ensure the animal receives proper nutrition and hydration to support recovery.

Zoonotic importance

Myiasis, the infestation of live vertebrates by fly larvae, holds significant zoonotic importance as it can affect both animals and humans, posing serious health risks. This condition is primarily seen in rural and tropical areas where hygiene and wound care may be inadequate. Humans, particularly those with open wounds or compromised health, are at risk of myiasis, which can result in painful lesions, secondary bacterial infections, and in severe cases, systemic illness. Understanding and addressing myiasis through improved hygiene, wound care, and pest control are crucial for public health and animal welfare.

Summary

Myiasis/Fly strike, an infestation of animals by fly larvae, is a significant concern for both pets and livestock, causing distress and serious health issues. These parasitic larvae, typically from blowflies, deposit their eggs on wounds, sores, or in moist areas of the host's body. Once hatched, the larvae feed on the host's tissue, leading to painful lesions, infections, and in severe cases, systemic illness or death. Prevention and early detection are crucial, involving proper wound care, maintaining clean living environments, and using insect repellents or fly control measures. Veterinary intervention is often necessary to treat infestations, emphasizing the importance of regular health checks and prompt medical attention to affected animals.

Check out previous post - The Buzzkill (Flies)