Parasitic infections are one of the main causes of disease and loss of productivity on livestock farms around the world, which is why their control is absolutely necessary.

Cattle are natural hosts for a large number of internal parasites. On this occasion, we will focus on three of the causative agents of digestive pathologies in dairy cows: cryptosporidiosis, coccidiosis and gastrointestinal nematodosis. Also, we will leave you with recommendations to control these parasites in dairy cattle farms.

• Bovine cryptosporidiosis.
• Coccidiosis.
• Gastrointestinal Nematodosis.
• Importance of deworming in dairy herds.
• Bovine cryptosporidiosis.
• Preventive measures for parasite control.
• Conventional dewormers and their obstacles.
• AMBiotec sheep deworming program.
• How to administer AMBiotec products.
• Conclusions

Bovine cryptosporidiosis.

It is a parasitic disease of worldwide distribution, whose main clinical sign is diarrhea in neonatal calves. This disease not only represents a sanitary and animal production problem, but it is also a zoonosis and there is a possibility that bovines act as a source of contagion, transmitting the parasite to the human population through food and water.

Bovine cryptosporidiosis is a self-limiting disease, in which clinical manifestations diminish between the 3rd and 4th week of the animal's life. This does not mean that there is no excretion of oocysts, but that the organism of a young bovine will manage to generate local immunity to counteract the effect of the parasite and begin the regeneration of enterocytes.

Causal Agent

About 80% of cases are caused by the protozoan Cryptosporidium parvum, although infections caused by C. bovis, C. ryanae, C. andersoni can also be found, this variation depending on the geographical condition.

Localization of the parasite in the host.

Parasitosis is localized in the small intestine, with special predilection for the final parts of the jejunum and ileum, although occasionally it can affect the large intestine or the entire intestinal tract.

It´s localization is intracellular, in the luminal border of enterocytes.

Sources of infection and routes of transmission

In ruminants, the main source of infection is the faeces of neonatal animals with diarrhoea, which can excrete between 1 and 10 million oocysts per gram of faeces.

Adult cattle act as asymptomatic carriers and can shed oocysts into the environment via their faeces.

Transmission of Cryptosporidium spp. to calves occurs at birth, from their mother, during calving or in the environment of the calving area. The minimum number of oocysts necessary to produce clinical manifestations is 25 oocysts/animal.

On the other hand, wild animals are also an important source of gastrointestinal parasite infection.

Accordingly, transmission of the parasite can occur by:

• Direct contact.
• Oral-fecal between calves.
• Fomites (instruments, tools, etc.).
• Humans as a mechanical vector.

Symptomatology.

The main clinical sign is diarrhea.

Depending on various factors such as age, immune status and environmental conditions, other clinical signs such as anorexia, abdominal pain, weight loss, prostration and fever may occur. If environmental conditions are adverse and farm management is not good, outbreaks with high mortality can occur.

Coccidiosis.

This name is often used to refer to the disease caused by eimeria. However, there are other parasites that belong to this subclass such as: Toxoplasma, Neospora and even crytosporidium. In this section, we will focus on eimeria as a cause of coccidiosis.

Like cryptosporidium, eimeria are cosmopolitan in distribution. They produce an intestinal infection that mainly affects young animals and causes diarrhea, sometimes bloody.

Causal Agent

Several species of the Eimeria family. Twenty-one different species have been described in cattle, although only 13 are recognized. The two most pathogenic species are Eimeria bovis and Eimeria zuernii (Ernst and Benz, 1986).

The incubation period of these protozoa is 15 to 20 days (Georgi, 1985). Immunity to coccidia persists for 3-4 months, so in the absence of a constant threat, reinfection is likely to occur.

Localization of the parasite in the host.

They are intracellular and invade the epithelium of the small intestine, especially the second half (jejunum and ileum).

Sources of infection and routes of transmission.

Cattle become infected by ingesting oocysts with feed or water.

The main source of infection of this disease in calves is feces with oocysts, initially excreted by cows and later, and in greater quantity, by young animals. Exposure to coccidia is almost immediate from birth; however, the critical stage of manifestation occurs between the 4th and 7th week of the animal's life.

On the other hand, oocysts resist several months in humid and shady places, especially in common areas of drinkers, feeders and in the bedding, where a high number accumulates, so that in intensive farms clinical outbreaks can occur at any time.

The immune response to coccidia depends on the level and time of exposure. It is common for animals that have had the disease to be resistant to reinfection (provided there is no nutritional, management or sanitary interference). In addition, immunity is not sterilizing, since resistant animals continue to excrete oocysts into the environment, thus contributing to the continuity of the infection in livestock farms.

Symptomatology.

Coccidiosis usually occurs in young animals, from 3 to 6 weeks of age, although there can also be outbreaks in animals of 5 or more months.

In mild cases, the animals present diarrhea with or without blood, and may have anorexia and decay for a few days.

In severe cases, feces are more liquid and may contain mucus and/or blood, or directly pieces of intestinal mucosa. Tenesmus and even rectal prolapse may be seen due to strong straining. Animals start with weight loss, dehydration, prostration, apathy, which may end in death.

Massive ingestion of the oocyst causes infection of large numbers of epithelial cells, causing considerable damage before the sexual cycle of the parasite is completed. That is, an animal can develop the disease with diarrhea without detecting oocysts in the feces.

Gastrointestinal Nematodosis.

Gastrointestinal nematodes are the most frequent parasites worldwide, causing gastroenteritis, processes of chronic course and low mortality. It is mainly characterized by digestive disturbances, growth retardation and decreased production. The intensity of parasitization varies with age and especially with the production system.

Causal agent.

Nematodes are cylindrical worms that inhabit the digestive tract of cattle and other ruminants. There are several families and genera, among which the following stand out: Trichostrongylidae (haemonchus, trichostrongylus, coperia, Ostertagia), Molineidae (Nematodirus) Ancylostomatidae (bunostomun) and Strongylidae (Oesophagastomum), Trichuridae (trichuris).

Localization of the parasite in the host.

Nematodes inhabit the abomasum (genera Ostertagia, Haemonchus and Trichostrongylus), small intestine (Trichostrongylus, Cooperia, Nematodirus, Bunostomum, Strongyloides) and large intestine (Oesophagastomum, Trichuris).

Generally, infections are mixed, involving two or more genera and several species.

Sources of infection and routes of transmission.

Nematodes are parasites that are in the environment and can contaminate animals through the ingestion of infectious eggs. In other words, the route of transmission is oral.

Symptomatology.

Symptomatology includes: inappetence, lethargy, weight loss, abdominal distension, diarrhea, dehydration, bristly hair (long, dry and brittle), pale mucous membranes, edema and increased heart and respiratory rate.

In addition, when parasitosis becomes chronic, it usually goes unnoticed, causing great economic losses that remain hidden in the decreased productivity of the herd

Importance of deworming in dairy herds.

The three parasitoses described above affect dairy cows at various stages of their life cycle. Mainly, young animals are more affected, and then we can see how the animal's organism is able to generate immunity to counteract the effects of the parasites. However, this immunity can be...