Dictyocaulus
Encyclopedia
Dictyocaulus is a genus
of nematode
parasites of the bronchial tree of horse
s, sheep, goat
s, deer
, and cattle
. Dictyocaulus arnfeldii is the lungworm
of horse
s, and Dictyocaulus viviparus is the lungworm affecting ruminant
s.
The parasite has a simple but interesting life cycle, with dipersal facilitated by a fungus.
Adult D. viviparus worms reside in the bronchial tree of the animal's lung
s. They lay eggs into the airways (bronchi). These eggs are coughed up and subsequently swallowed by the host. The eggs hatch into Stage 1 larvae (L1) in the gastrointestinal tract
of the ruminant
host. These L1 larvae are shed in the feces
or manure
. In the feces, larvae mature through two stages and become infective as L3 stage larvae. Cattle feces supports the growth of Pilobolus
sp. fungi. The L3 larvae of D. viviparus invade the inside of these fungi, and wait in the fungal sporangium
. When the fungus sporulates, the larvae are dispersed as much as 10 feet in a pasture.
Cattle grazing then ingest the L3 larvae. These larvae go through the intestinal system and penetrate the intestinal wall. They use the lymphatic system
to reach the mesenteric lymph node
s, where they mature once again into L4 stage larvae. The L4 larvae use the blood supply and the lymphatic system to reach the lungs, where they become adults. The life cyle is completed.
, fenbendazole
, febantel and other anthelmintics. Pasture management should take into consideration the infectiveness of these organisms.
s. Donkeys usually show no disease and can be silent carriers (and shedders) of this parasite, which causes clinical signs in horses. Routine deworming of horses and donkeys may help prevent cross infection when kept together. Pastures that housed donkeys may be infected with lungworm larvae. As a result, horses and donkeys should not be grazed together. These drugs are given with three weeks intervals between treatments.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of nematode
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...
parasites of the bronchial tree of horse
Horse
The horse is one of two extant subspecies of Equus ferus, or the wild horse. It is a single-hooved mammal belonging to the taxonomic family Equidae. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature into the large, single-toed animal of today...
s, sheep, goat
Goat
The domestic goat is a subspecies of goat domesticated from the wild goat of southwest Asia and Eastern Europe. The goat is a member of the Bovidae family and is closely related to the sheep as both are in the goat-antelope subfamily Caprinae. There are over three hundred distinct breeds of...
s, deer
Deer
Deer are the ruminant mammals forming the family Cervidae. Species in the Cervidae family include white-tailed deer, elk, moose, red deer, reindeer, fallow deer, roe deer and chital. Male deer of all species and female reindeer grow and shed new antlers each year...
, and cattle
Cattle
Cattle are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos primigenius...
. Dictyocaulus arnfeldii is the lungworm
Lungworm
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...
of horse
Horse
The horse is one of two extant subspecies of Equus ferus, or the wild horse. It is a single-hooved mammal belonging to the taxonomic family Equidae. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature into the large, single-toed animal of today...
s, and Dictyocaulus viviparus is the lungworm affecting ruminant
Ruminant
A ruminant is a mammal of the order Artiodactyla that digests plant-based food by initially softening it within the animal's first compartment of the stomach, principally through bacterial actions, then regurgitating the semi-digested mass, now known as cud, and chewing it again...
s.
Dictyocaulus viviparus: lungworm of cattle, deer
D. viviparus is the most common lungworm of cattle; the infection is also known as husk or parasitic bronchitis. Although classified as the same parasite, some people believe that the D. viviparus of deer and elk should be reclassified as a different species, including D. eckertii in New Zealand. However, both species have been shown capable of cross-infecting cattle and cervids (at least in New Zealand) .The parasite has a simple but interesting life cycle, with dipersal facilitated by a fungus.
Adult D. viviparus worms reside in the bronchial tree of the animal's lung
Lung
The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...
s. They lay eggs into the airways (bronchi). These eggs are coughed up and subsequently swallowed by the host. The eggs hatch into Stage 1 larvae (L1) in the gastrointestinal tract
Gastrointestinal tract
The human gastrointestinal tract refers to the stomach and intestine, and sometimes to all the structures from the mouth to the anus. ....
of the ruminant
Ruminant
A ruminant is a mammal of the order Artiodactyla that digests plant-based food by initially softening it within the animal's first compartment of the stomach, principally through bacterial actions, then regurgitating the semi-digested mass, now known as cud, and chewing it again...
host. These L1 larvae are shed in the feces
Feces
Feces, faeces, or fæces is a waste product from an animal's digestive tract expelled through the anus or cloaca during defecation.-Etymology:...
or manure
Manure
Manure is organic matter used as organic fertilizer in agriculture. Manures contribute to the fertility of the soil by adding organic matter and nutrients, such as nitrogen, that are trapped by bacteria in the soil...
. In the feces, larvae mature through two stages and become infective as L3 stage larvae. Cattle feces supports the growth of Pilobolus
Pilobolus
Pilobolus is a genus of fungi that commonly grows on herbivore dung.-Life cycle:The life cycle of Pilobolus begins with a black sporangium that has been discharged onto a plant substrate such as grass. A herbivorous animal such as a horse then eats the substrate, unknowingly consuming the...
sp. fungi. The L3 larvae of D. viviparus invade the inside of these fungi, and wait in the fungal sporangium
Sporangium
A sporangium is an enclosure in which spores are formed. It can be composed of a single cell or can be multicellular. All plants, fungi, and many other lineages form sporangia at some point in their life cycle...
. When the fungus sporulates, the larvae are dispersed as much as 10 feet in a pasture.
Cattle grazing then ingest the L3 larvae. These larvae go through the intestinal system and penetrate the intestinal wall. They use the lymphatic system
Lymphatic system
The lymphoid system is the part of the immune system comprising a network of conduits called lymphatic vessels that carry a clear fluid called lymph unidirectionally toward the heart. Lymphoid tissue is found in many organs, particularly the lymph nodes, and in the lymphoid follicles associated...
to reach the mesenteric lymph node
Lymph node
A lymph node is a small ball or an oval-shaped organ of the immune system, distributed widely throughout the body including the armpit and stomach/gut and linked by lymphatic vessels. Lymph nodes are garrisons of B, T, and other immune cells. Lymph nodes are found all through the body, and act as...
s, where they mature once again into L4 stage larvae. The L4 larvae use the blood supply and the lymphatic system to reach the lungs, where they become adults. The life cyle is completed.
Diagnosis of D. viviparus infection
- Microscope detection of L1 larvae in feces
- Microscope detection of eggs or larvae in the coughed up sputumSputumSputum is mucus that is coughed up from the lower airways. It is usually used for microbiological investigations of respiratory infections....
or bronchoalveolar lavageBronchoalveolar lavageBronchoalveolar lavage is a medical procedure in which a bronchoscope is passed through the mouth or nose into the lungs and fluid is squirted into a small part of the lung and then recollected for examination. BAL is typically performed to diagnose lung disease...
fluid from affected animal - Blood serology test for worm antigens (available in some countries / states)
Treatment of lungworm infections
Lungworms can be treated with ivermectin, albendazoleAlbendazole
Albendazole, marketed as Albenza, Eskazole, Zentel and Andazol, is a member of the benzimidazole compounds used as a drug indicated for the treatment of a variety of worm infestations. Although this use is widespread in the United States, the U.S. Food and Drug Administration has not approved...
, fenbendazole
Fenbendazole
Fenbendazole is a broad spectrum benzimidazole anthelmintic used against gastrointestinal parasites including roundworms, hookworms, whipworms, the taenia species of tapeworms, pinworms, aelurostrongylus, paragonimiasis, strongyles and strongyloides and can be administered to sheep, cattle,...
, febantel and other anthelmintics. Pasture management should take into consideration the infectiveness of these organisms.
D. arnfieldi in horses and donkeys
D. arnfieldi is similar to D. viviparus in cattle, but only affects equidEquus (genus)
Equus is a genus of animals in the family Equidae that includes horses, donkeys, and zebras. Within Equidae, Equus is the only extant genus. Like Equidae more broadly, Equus has numerous extinct species known only from fossils. This article deals primarily with the extant species.The term equine...
s. Donkeys usually show no disease and can be silent carriers (and shedders) of this parasite, which causes clinical signs in horses. Routine deworming of horses and donkeys may help prevent cross infection when kept together. Pastures that housed donkeys may be infected with lungworm larvae. As a result, horses and donkeys should not be grazed together. These drugs are given with three weeks intervals between treatments.