Fly strike in sheep is a condition where parasitic flies lay eggs on soiled wool or open wounds. After hatching, the maggots, bury themselves in the sheep’s wool and eventually under the sheep’s skin, feeding off their flesh. Once the larvae develop, flies continue to deposit eggs on to new or already infected sheep, starting the infection process over again. Sheep display symptoms such as agitation, odour and matted wool, all which further encourage the attraction of flies. Fly strike can be lethal for sheep due to ammonia poisoning.

Fly strike is problematic, not only causing loss or degradation of stock, but also requiring expenditure of both money and time for effective management. In Australia, "Lucilia cuprina" causes about 90% of infestations, and "Chrysomya rufifacies" is the most common secondary pest the targets wounds caused by "L. cuprina".

There are several preventative measures which are used to reduce the occurrence of flystrike in sheep flocks, these include:

- Controlling intestinal parasites to prevent scours and a suitable surface for flystrike

- Scheduled shearing and crutching

- Removing the tails of lambs at weaning

- Mulesing

- Preventative chemical treatments before fly infestation risk is high

- Breeding for traits that reduce the likelihood of infestation

- Removing or avoiding large maunure heaps or other sites attractive to the flies

- Using fly traps near the flock to attract and kill any local flies, helping to minimise the local populations. NB: Traps often emit a pungent smell and are best placed away from human activity.

None of these measures completely stop the occurrence of fly strike in sheep, and regular treatment is still necessary.

Wound myiasis occurs when fly larvae infest open wounds. It has been a serious complication of war wounds in tropical areas, and is sometimes seen in neglected wounds in most parts of the world. Predisposing factors include poor socioeconomic conditions, extremes of age, neglect, mental disability, psychiatric illness, alcoholism, diabetes, and vascular occlusive disease.

There has been anecdotal evidence provided by Elaine Ingham according to which susceptibility to facial eczema in cattle is related to nutrient deficiency of forage. The experiment, which Ingham conducted, showed that by improving soil biology the forage had better nutrient qualities and was associated with an elimination of the disease.

Human "F. hepatica" infection is determined by the presence of the intermediate snail hosts, domestic herbivorous animals, climatic conditions and the dietary habits of man. Sheep, goats and cattle are considered the predominant animal reservoirs. While other animals can be infected, they are usually not very important for human disease transmission. On the other hand, some authors have observed that donkeys and pigs contribute to disease transmission in Bolivia. Among wild animals, it has been demonstrated that the peridomestic rat ("Rattus rattus") may play an important role in the spread as well as in the transmission of the parasite in Corsica. In France, nutria ("Myocastor coypus") was confirmed as a wild reservoir host of "F. hepatica". Humans are infected by ingestion of aquatic plants that contain the infectious cercariae. Several species of aquatic vegetables are known as a vehicle of human infection. In Europe, "Nasturtium officinale" (common watercress), "Nasturtium silvestris", "Rorippa amphibia" (wild watercress), "Taraxacum dens leonis" (dandelion leaves), "Valerianella olitoria" (lamb's lettuce), and "Mentha viridis" (spearmint) were reported as a source of human infections. In the Northern Bolivian Altiplano, some authors suggested that several aquatic plants such as bero-bero (watercress), algas (algae), kjosco and tortora could act as a source of infection for humans. Because "F. hepatica" cercariae also encyst on water surface, humans can be infected by drinking of fresh untreated water containing cercariae. In addition, an experimental study suggested that humans consuming raw liver dishes from fresh livers infected with juvenile flukes could become infected.

Myiasis of the human eye or ophthalmomyiasis can be caused by "Hypoderma tarandi", a parasitic botfly of caribou. It is known to lead to uveitis, glaucoma, and retinal detachment.

Human ophthalmomyiasis, both external and internal, has been caused by the larvae of the botfly.

Mechanisms of resistance have been studied by several authors in different animal species. These studies may help to better understand the immune response to "F. hepatica" in host and are necessary in development of vaccine against the parasite. It has been established that cattle acquire resistance to challenge infection with "F. hepatica" and "F. gigantica" when they have been sensitized with primary patent or drug-abbreviated infection. Resistance to fasciolosis was also documented in rats. On the other hand, sheep and goats are not resistant to re-infection with "F. hepatica". However, there is evidence that two sheep breeds, in particular Indonesian thin tail sheep and Red maasai sheep, are resistant to "F. gigantica". No reports concerning the resistance in humans are available.

By one author's count, 257 human cases of "Thelazia callipaeda" had been reported worldwide by the year 2000, though thelaziasis is still considered to be a rare disease.

Various livestock and wildlife surveys suggest that thelaziasis is quite common among animals.

- A slaughterhouse survey in Canada found that about one-third (32%) of cattle over an 8-month period were infested with eyeworms.

- A survey of horses in Kentucky revealed a 42% rate of infestation with "Thelazia lacrymalis".

- In Wyoming and Utah, a survey of hunter-harvested mule deer found 15% to be infested by "Thelazia californiensis".

- A survey of various sites in Italy found 23-60% of dogs, 5% of foxes and 4 out of 4 cats to be infested with "Thelazia callipaeda".

Facial eczema, FE, is a disease that mainly affects ruminants such as cattle, sheep, deer, goats and South American camelids (alpaca, llamas).

It is caused by the fungus "Pithomyces chartarum" that under favorable conditions can rapidly disseminate in pastures. The fungus requires warm humid weather with night time temperatures of over 13 °C (55 °F) for several days, and litter at the bottom of the sward.

"Pithomyces chartarum" occurs worldwide but is a problem predominantly where farm animals are intensively grazed, especially in New Zealand.

The spores of the fungus release the mycotoxin sporidesmin in the gastrointestinal tract, causing a blockage in the bile ducts that leads to injury of the liver. Bile, chlorophyll and other waste products consequently build up in the bloodstream causing photo sensitivity of the skin especially that exposed to direct sunlight. This in turn causes severe skin irritation that the animal attempts to relieve by rubbing its head against available objects, resulting in peeling of the skin.

The large family of fungi that produce mycotoxins, of which sporidesmin is one, live mainly on ryegrasses and can cause significant problems in grazing animals. Sporidesmin can lower an animals immunity and affect total production in farm animals, and, when taken in larger quantities, can result in death.

The clinical symptoms of FE are distressing: restlessness, frequent urination, shaking, persistent rubbing of the head against objects (e.g. fences, trees etc.), drooping and reddened ears, swollen eyes, and avoidance of sunlight by seeking shade. Exposed areas of skin develop weeping dermatitis and scabs that can become infected and attractive to blow-fly causing myiasis.

Because "O. sericea" is both frequently encountered and relatively palatable to livestock, it is an important cause of economic losses in livestock production. Keeping livestock away from locoweed infested pasture in spring and fall when grass and other forbs are not actively growing is recommended. Another suggested remedy is to provide palatable supplemental nutrients if animals are to be kept in infested pasture. These remedies take into account livestock preference for locoweed during seasons when grass is dry and not very nutritious. Conditioned food aversion has been used experimentally to discourage livestock from eating it. In horses, a small study has shown promising results using lithium chloride as the aversive agent.

Thelaziasis (occasionally spelled "thelaziosis") is the term for infestation with parasitic nematodes of the genus "Thelazia". The adults of all "Thelazia" species discovered so far inhabit the eyes and associated tissues (such as eyelids, tear ducts, etc.) of various mammal and bird hosts, including humans. Thelazia nematodes are often referred to as "eyeworms."

Locoweed (also crazyweed and loco) is a common name in North America for any plant that produces swainsonine, a phytotoxin harmful to livestock. Worldwide, swainsonine is produced by a small number of species, most in three genera of the flowering plant family Fabaceae: "Oxytropis" and "Astragalus" in North America, and "Swainsona" in Australia. The term locoweed usually refers only to the North American species of "Oxytropis" and "Astragalus", but this article includes the other species as well. Some references may list "Datura stramonium" as locoweed.

Locoweed is relatively palatable to livestock, and some individual animals will seek it out. Livestock poisoned by chronic ingestion of large amounts of swainsonine develop a medical condition known as locoism (also swainsonine disease, swainsonine toxicosis, locoweed disease, and loco disease; North America) and pea struck (Australia). Locoism is reported most often in cattle, sheep, and horses, but has been reported also in elk and deer. It is the most widespread poisonous plant problem in the western United States. Agricultural Research Service and New Mexico State University scientists have been collaborating since 1990 to help solve the problem that locoweed presents to livestock farmers. The research involved identifying the fungal species that produces the locoweed toxins, pinpointing levels of toxicity in animals once they have ingested locoweed, observing the effects of locoweed toxins on livestock’s reproduction and grazing preferences, etc. Together, the scientists assembled a grazing management scheme to help farmers avoid the poisonous locoweed.

Most of the 2000 species of "Astragalus", including many that are commonly known as locoweeds, do not produce swainsonine. Some species, including a few that produce swainsonine, accumulate selenium. This has led to confusion between swainsonine poisoning and selenium poisoning due to this genus.

Amphistomiasis in farm and wild mammals is due to infection of paramphistomes, such as the species of "Paramphistomum", "Calicophoron", "Cotylophoron", "Pseudophisthodiscus", etc. These are essentially rumen flukes, of which "Paramphistomum cervi" is the most notorious in terms of prevalence and pathogenicity. Infection occurs through ingestion of contaminated vegetables and raw meat, in which the viable infective metacercaria are deposited from snails, which are the intermediate hosts. The immature flukes are responsible for destroying the mucosal walls of the alimentary tract on their way to growing into adults. It is by this fervent tissue obliteration that the clinical symptoms are manifested. The adult flukes, on the other hand, are quite harmless, as they merely prepare for reproduction.

The zoonotic infection in human is caused by "G. discoides" and "W. watsoni" which are essentially intestinal flukes. The disease due to "G. discoides" is more specifically termed gastrodiscoidiasis. In their natural hosts such as pigs and monkeys, their infection in asymptomatic, but human infection is prevalent, by which they cause serious health problems, characterised by diarrhoea, fever, abdominal pain, colic, and an increased mucous production. In extreme situations such as in Assam, India, a number of mortality among children is attributed to this disease.

Human milk sickness is uncommon today in the United States. Current practices of animal husbandry generally control the pastures and feed of cattle, and the pooling of milk from many producers lowers the risk of tremetol present in dangerous amounts. The poison tremetol is not inactivated by pasteurization. Although extremely rare, milk sickness can occur if a person drinks contaminated milk or eats dairy products gathered from a single cow or from a smaller herd that has fed on the white snakeroot plant. There is no cure, but treatment is available.

Amphistomiasis is considered a neglected tropical disease, with no prescription drug for treatment and control. Therefore, management of infestation is based mainly on control of the snail population, which transmit the infective larvae of the flukes. However, there are now drugs shown to be effective including resorantel, oxyclozanide, clorsulon, ivermectin, niclosamide, bithional and levamisole. An in vitro demonstration shows that plumbagin exhibits high efficacy on adult flukes. Since the juvenile flukes are the causative individuals of the disease, effective treatment means control of the immature fluke population. Prophylaxis is therefore based on disruption of the environment (such as proper drainage) where the carrier snails inhabit, or more drastic action of using molluscicides to eradicate the entire population. For treatment of the infection, drugs effective against the immature flukes are recommended for drenching. For this reason oxyclozanide is advocated as the drug of choice. It effectively kills the flukes within a few hours and it effective against the flukes resistant to other drugs. The commercially prescribed dosage is 5 mg/kg body weight or 18.7 mg/kg body weight in two divided dose within 72 hours. Niclosamide is also extensively used in mass drenching of sheep. Successfully treated sheep regain appetite within a week, diarrhoea stops in about three days, and physiological indicators (such as plasma protein and albumin levels) return to normal in a month.

Herbicide applications aimed to reduce ryegrass population have been successful in reducing the risk of ARGT but have undesirable effects such as rapid reduction in pasture productivity and increase in ryegrass herbicide resistance.

A recently released biological control agent, the twist fungus, has been demonstrated to be effective in reducing the risk ARGT without the need of controlling ryegrass. The first use of the twist fungus inoculum was in 1997.

Lungworms are parasitic nematode worms of the order Strongylida that infest the lungs of vertebrates. The name is used for a variety of different groups of nematodes, some of which also have other common names; what they have in common is that they migrate to their hosts' lungs or respiratory tracts, and cause bronchitis or pneumonia. The lungworm will gradually damage the airways or lung tissue by inciting an inflammatory reaction inside the tissue. Ultimately, the parasites survive and reproduce in the respiratory tissues. The category is thus more a descriptive than a precisely taxonomic one.

The most common lungworms belong to one of two groups, the superfamily Trichostrongyloidea or the superfamily Metastrongyloidea, but not all the species in these superfamilies are lungworms.

The lungworms in the superfamily Trichostrongyloidea include several species in the genus "Dictyocaulus" which infest hoofed animals, including most common domestic species. Different species are found in cattle and deer ("D. viviparus"), donkeys and horses ("D. arnfeldi"), and sheep and goats ("D. filaria"). These animals have direct life-cycles. The lungworms in the superfamily Metastrongyloidea include species that infest a wider range of mammals, including sheep, goats and pigs but also cats and dogs.

These include "Metastrongylus elongatus (apri)", found in pigs; "Oslerus osleri" found in dogs; and "Aelurostrongylus abstrusus" found in cats. Some of these have indirect, and complex, life-cycles; several of them involve slugs or snails as intermediate hosts, where the habit of sniffing at slug trails, or even licking them, causes the parasite egg to enter the dog's respiratory tract. In the case of "A. abstrusus" the cat is normally infected by eating a bird or rodent that has itself eaten the original host.

Lungworm infestations can cause significant distress to the animal but are usually treatable with drugs.

If infected with lungworm parasite, an anti-parasite drug must be administered.

In the case of a severe reaction, an anti-inflammatory drug of corticosteroids may be given for a brief period (3 to 10 days).

To treat tissue inflammation, Prednisone is usually given (5–10 days). However, there are some side effects such as increased urination or appetite.

The drugs fenbendazole or moxidectin are usually administered to kill the parasite.

There are several different lungworm parasites that have been identified. Although they all originate from the lungworm parasite, they are treated somewhat differently and requires a combination of various drugs to treat the parasite.

Although coenurosis is more commonly associated with domestic animals, it has also been documented in wildlife. It has been found in mountain ungulates in the French Alps. It is believed that the ungulates are being contaminated by infected sheepdogs. Understanding how this disease is transmitted from sheepdogs to wild animals is important in managing the spread of this potentially dangerous zoonotic disease. A potential management strategy would be for farmers to properly dispose of carcasses that they find on their land. In wild gelada monkeys in Ethiopia, coenurosis was found to affect the fitness of these primates. Mortality increased and fertility was inhibited. The disease has also been documented in wild sheep and other ruminants and rarely documented in rodents, horses, and cats. Very few cases have been identified but this could be due to limited research on wild coenurosis. Animals infected with this disease tend to hide or take cover from predators and therefore may not be seen by humans. However, coenurosis has been known to increase mortality and decrease fertility in wild animal populations.

In order to control for the disease, the "Lymnaea" spp snails, which are the intermediate host for the liver flukes, need to be controlled. There are three ways that have proven most effective when controlling the snail populations:

- The first is by treating pastures and water channels with copper sulfate. This method is not always practical, because it is too expensive to treat in large areas. Lack of cooperation between neighbors is also a problem, snails are easily transported, and treated pastures become re-infested by neighboring fields and streams.

- Drenching the sheep with carbon tetra-chloride in paraffin oil has proven to be an alternative. However, drenching in more than recommended doses can be fatal, by causing liver damage, which could initiate the disease in sheep carrying "B. oedematiens" spores.

- Drainage is an effective option to eliminate the snails. However, draining the places where the grass grows eliminates a source of food for the sheep and creates other unwanted problems.

Myiasis is a parasitic infestation caused by larvae of several fly species. Diagnosis and treatment are generally quite simple. This infestation is, however, rarely seen in the vulvar area. Infestation of vulvar area with larvae and maggots is called vulvar myiasis. Very few cases have been described in literature.

Most occurrences are found in areas that lack adequate sanitation and include Southeast Asia, West Africa, and East Africa.

As of 2009, loiasis is endemic to 11 countries, all in western or central Africa, and an estimated 12–13 million people have the disease. The highest incidence is seen in Cameroon, Republic of the Congo, Democratic Republic of Congo, Central African Republic, Nigeria, Gabon, and Equatorial Guinea. The rates of "Loa loa" infection are lower but it is still present in and Angola, Benin, Chad and Uganda. The disease was once endemic to the western African countries of Ghana, Guinea, Guinea Bissau, Ivory Coast and Mali but has since disappeared.

Throughout "Loa loa"-endemic regions, infection rates vary from 9 to 70 percent of the population. Areas at high risk of severe adverse reactions to mass treatment (with Ivermectin) are at present determined by the prevalence in a population of >20% microfilaremia, which has been recently shown in eastern Cameroon (2007 study), for example, among other locales in the region.

Endemicity is closely linked to the habitats of the two known human loiasis vectors, "Chrysops dimidiata" and "C. silicea".

Cases have been reported on occasion in the United States but are restricted to travelers who have returned from endemic regions.

In the 1990s, the only method of determining "Loa loa" intensity was with microscopic examination of standardized blood smears, which is not practical in endemic regions. Because mass diagnostic methods were not available, complications started to surface once mass ivermectin treatment programs started being carried out for onchocerciasis, another filariasis. Ivermectin, a microfilaricidal drug, may be contraindicated in patients who are co-infected with loiasis and have associated high microfilarial loads. The theory is that the killing of massive numbers of microfilaria, some of which may be near the ocular and brain region, can lead to encephalopathy. Indeed, cases of this have been documented so frequently over the last decade that a term has been given for this set of complication: neurologic serious adverse events (SAEs).

Advanced diagnostic methods have been developed since the appearance the SAEs, but more specific diagnostic tests that have been or are currently being development (see: Diagnostics) must to be supported and distributed if adequate loiasis surveillance is to be achieved.

There is much overlap between the endemicity of the two distinct filariases, which complicates mass treatment programs for onchocerciasis and necessitates the development of greater diagnostics for loiasis.

In Central and West Africa, initiatives to control onchocerciasis involve mass treatment with Ivermectin. However, these regions typically have high rates of co-infection with both "L. loa" and "O. volvulus", and mass treatment with Ivermectin can have severe adverse effects (SAE). These include hemorrhage of the conjunctiva and retina, heamaturia, and other encephalopathies that are all attributed to the initial L. loa microfilarial load in the patient prior to treatment. Studies have sought to delineate the sequence of events following Ivermectin treatment that lead to neurologic SAE and sometimes death, while also trying to understand the mechanisms of adverse reactions to develop more appropriate treatments.

In a study looking at mass Ivermectin treatment in Cameroon, one of the greatest endemic regions for both onchocerciasis and loiasis, a sequence of events in the clinical manifestation of adverse effects was outlined.

It was noted that the patients used in this study had a "L. loa" microfilarial load of greater than 3,000 per ml of blood.

Within 12–24 hours post-Ivermectin treatment (D1), individuals complained of fatigue, anorexia, and headache, joint and lumbar pain—a bent forward walk was characteristic during this initial stage accompanied by fever. Stomach pain and diarrhea were also reported in several individuals.

By day 2 (D2), many patients experienced confusion, agitation, dysarthria, mutism and incontinence. Some cases of coma were reported as early as D2. The severity of adverse effects increased with higher microfilarial loads. Hemorrhaging of the eye, particularly the retinal and conjunctiva regions, is another common sign associated with SAE of Ivermectin treatment in patients with "L. loa" infections and is observed between D2 and D5 post-treatment. This can be visible for up to 5 weeks following treatment and has increased severity with higher microfilarial loads.

Haematuria and proteinuria have also been observed following Ivermectin treatment, but this is common when using Ivermectin to treat onchocerciasis. The effect is exacerbated when there are high "L. loa" microfilarial loads however, and microfilariae can be observed in the urine occasionally. Generally, patients recovered from SAE within 6–7 months post-Ivermectin treatment; however, when their complications were unmanaged and patients were left bed-ridden, death resulted due to gastrointestinal bleeding, septic shock, and large abscesses.

Mechanisms for SAE have been proposed. Though microfilarial load is a major risk factor to post-Ivermectin SAE, three main hypotheses have been proposed for the mechanisms.

The first mechanism suggests that Ivermectin causes immobility in microfilariae, which then obstructs microcirculation in cerebral regions. This is supported by the retinal hemorrhaging seen in some patients, and is possibly responsible for the neurologic SAE reported.

The second hypothesis suggests that microfilariae may try to escape drug treatment by migrating to brain capillaries and further into brain tissue; this is supported by pathology reports demonstrating a microfilarial presence in brain tissue post-Ivermectin treatment.

Lastly, the third hypothesis attributes hypersensitivity and inflammation at the cerebral level to post-Ivermectin treatment complications, and perhaps the release of bacteria from L. loa after treatment to SAE. This has been observed with the bacteria "Wolbachia" that live with "O. volvulus".

More research into the mechanisms of post-Ivermectin treatment SAE is needed to develop drugs that are appropriate for individuals suffering from multiple parasitic infections.

One drug that has been proposed for the treatment of onchocerciasis is doxycycline. This drug has been shown to be effective in killing both the adult worm of "O. volvulus" and "Wolbachia", the bacteria believed to play a major role in the onset of onchocerciasis, while having no effect on the microfilariae of "L. loa". In a study done at 5 different co-endemic regions for onchocerciasis and loiasis, doxycycline was shown to be effective in treating over 12,000 individuals infected with both parasites with minimal complications. Drawbacks to using Doxycycline include bacterial resistance and patient compliance because of a longer treatment regimen and emergence of doxycycline-resistant "Wolbachia". However, in the study over 97% of the patients complied with treatment, so it does pose as a promising treatment for onchocerciasis, while avoiding complications associated with L. loa co-infections.

Human loiasis geographical distribution is restricted to the rain forest and swamp forest areas of West Africa, being especially common in Cameroon and on the Ogooué River. Humans are the only known natural reservoir. It is estimated that over 10 million humans are infected with "Loa loa" larvae.

An area of tremendous concern regarding loiasis is its co-endemicity with onchocerciasis in certain areas of west and central Africa, as mass ivermectin treatment of onchocerciasis can lead to serious adverse events (SAEs) in patients who have high "Loa loa" microfilarial densities, or loads. This fact necessitates the development of more specific diagnostics tests for "Loa loa" so that areas and individuals at a higher risk for neurologic consequences can be identified prior to microfilaricidal treatment. Additionally, the treatment of choice for loiasis, diethylcarbamazine, can lead to serious complications in and of itself when administered in standard doses to patients with high "Loa loa" microfilarial loads.

Coenurosis (a.k.a. Caenurosis and Coenuriasis, gid or sturdy in the vernacular) is a parasitic infection that develops in the intermediate hosts of some tapeworm species ("Taenia multiceps", "T. serialis, T. brauni," or "T. glomerata") and are caused by the coenurus, the larval stage of these worms. This disease occurs mainly in sheep and other ungulates, but occasionally can occur in humans too by accidental ingestion of worms' eggs.

Adult worms of these species develop in the small intesine of the definitive hosts (dogs, foxes, and other canids), causing a disease from the group of taeniasis. Humans cannot be definitive hosts for these species of tapeworms.

The first sign of a foot-rot infection is when the skin between the claws of the hoof begins to swell (cellulitis). Swelling usually appears 24 hours after infection. The skin between the toes may be very red and tender and the toes may separate because of all the swelling. This is very painful to the animal and can cause lameness. The animal may also have a raised body temperature. A crack can develop along the infected part and is yellow in color. The foot will have a foul odor. Tendons and joints in the area can become infected, which is much harder to treat. A condition known as "super foot rot" is seen in some animals. Super foot rot infection occurs much faster and is usually much more severe. Most normal foot rot treatments will not cure this foot rot and a veterinarian should be contacted immediately.

Vaccines have been developed, but their efficacy is questionable and the immunity they provide is of short duration.