NASAL SCHISTOSOMIASIS OR SNORING DISEASE (NAKRA) IN CATTLE
Nasal schistosomosis or snoring disease, caused by Schistosoma nasale, is a snail borne trematode infection adversely affects the health and production of domestic livestock in various parts of India.
Schistosomiasis is a snail-borne trematode infection of domestic animals and man in different parts of Asia and Africa. The freshwater snail Indoplanorbis exustus acts as intermediate host . This disease is generally chronic in nature and symptoms in majority of animals are insufficient to distinguish the illness from other debilitating infections . It is widely distributed in cattle, buffalo, sheep and goat in India . Snoring disease was reported from Tamil Nadu, Karnataka, Andhra Pradesh, West Bengal, Assam, Bihar, Orissa and Maharashtra . Affected cattle shows rhinitis, profuse mucopurulent nasal discharge which is clinically manifested by sneezing, dyspnoea and snoring. Chronic infections show proliferation of nasal epithelium as granuloma and small abscesses containing eggs. In this post tentative diagnosis was made on the basis of snorning respiratory sounds and the presence of nodular lesions in nasal cavity and adjunct areas
Life Cycle, Transmission, and Epidemiology:——-
Schistosomes live in the mesenteric and hepatic veins of the host (except for S nasale, which lives in the nasal veins), where they feed on blood and produce eggs with a characteristic terminal or lateral spine. Eggs passed in the feces must be deposited in water if they are to hatch and release miracidia, which invade suitable water snails and develop through primary and secondary sporocysts to become cercariae. When fully mature, the cercariae leave the snail and swim freely in the water, where they remain viable for several hours. Ruminants are usually infected with cercariae by penetration of the skin, although infection may be acquired orally while animals are drinking. During penetration, cercariae develop into schistosomula, which are transported via the lymph and blood to their predilection sites. The prepatent period varies according to the species but is generally 45–70 days.
The occurrence of cattle schistosomes within their range is discontinuous, depending on the presence of intermediate snail hosts, their level of infection, and the frequency of water contacts. In areas where conditions are favorable, prevalence rates of infections in cattle may be 40%–70% and commonly higher.
The increased host range of the hybrid parasites and changes in host distribution seen in Africa may have a direct impact on transmission of these schistosomes. Laboratory hybrids have been observed to acquire enhanced characteristics such as infectivity, fecundity, and growth rates.
There is strong evidence that acquired immunity to schistosome infection in cattle exists. This immunity mainly acts through suppression of worm fecundity. Examination of naturally infected animals has shown that partial protection against reinfection also occurs, and acquired resistance to schistosomes is of major importance in the regulation of infection intensity in the field.
Clinical Findings and Lesions:———–
Nasal schistosomiasis is associated with cauliflower-like growths on the nasal mucosa, causing partial obstruction of the nasal cavity and snoring sounds when breathing. Hemorrhagic and/or mucopurulent nasal discharge is a common feature. Adult flukes are found in the blood vessels of the nasal mucosa, but again, the main pathogenic effects are associated with the eggs, which cause abscesses in the mucosa. The abscesses rupture and release eggs and pus into the nasal cavity, which eventually leads to extensive fibrosis. In addition, large granulomatous growths are common on the nasal mucosa and occlude the nasal passages and cause dyspnea.
Visceral Schistosomiasis:
In the great majority of cases, visceral schistosomiasis in endemic areas is subclinical and characterized by a high prevalence of low to moderate worm burdens in the cattle population. Although few or no overt clinical signs may be recognized in the short term, high prevalence rates of chronic schistosome infections cause significant losses on a herd basis. These losses are due to less easily recognizable effects on growth and productivity, as well as increased susceptibility to other parasitic and bacterial diseases.
Occasional outbreaks of clinical intestinal schistosomiasis due to S mattheei, S bovis, or S spindale have been reported. They are usually restricted to young livestock and adult animals undergoing relatively heavy primary infections under conditions of intensive transmission. The disease is characterized by diarrhea, weight loss, anemia, hypoalbuminemia, hyperglobulinemia, and severe eosinophilia that develop after the onset of egg excretion. Severely affected animals deteriorate rapidly and usually die within a few months of infection, while those less heavily infected develop chronic disease with growth retardation.
In the intestinal and hepatic forms, adult flukes are found in the portal, mesenteric, and intestinal submucosal and subserosal veins. However, the main pathologic effects are associated with the eggs. In the intestinal form, passage of eggs through the gut wall causes the lesions, while in the hepatic form, granulomas form around eggs trapped in the tissues. Other hepatic changes include medial hypertrophy and hyperplasia of the portal veins, development of lymphoid nodules and follicles throughout the organ, and periportal fibrosis in more chronic cases. Extensive granuloma formation also is seen in the intestine. In severe cases, numerous areas of petechiation and diffuse hemorrhage are seen in the mucosa, and large quantities of discolored blood may be found in the intestinal lumen. Frequently, the parasitized blood vessels are dilated and tortuous. Vascular lesions also may be found in the lungs, pancreas, and bladder of heavily infected animals.
The hybridization events reported between animal and human schistosomes may result in phenotypic characteristics that influence pathology (and drug sensitivity).
Diagnosis:
Because signs and history alone are insufficient to distinguish visceral schistosomiasis from other debilitating diseases, diagnosis should be confirmed by the presence and identification of eggs in the feces of the infected animal. At necropsy, macroscopic examination of the mesenteric veins for the presence of adult worms or microscopic examination of scrapings of the intestinal mucosa or of crushed liver tissue (both for eggs) may prove easier.
Schistosoma bovis egg
Courtesy of Francis McNeilly.
Eggs of S bovis, S curassoni, and S mattheei are spindle-shaped. Because of the interspecific hybridization between S bovis and S curassoni and the natural hybridization between S haematobium and S mattheei, S bovis, and S curassoni, eggs of intermediate morphology may be seen. The eggs of S spindale are more elongated and flattened on one side, and those of S nasale are boomerang-shaped. The oval eggs of S japonicum are relatively small, with a rudimentary spine.
Very low fecal egg excretion is commonly seen in chronic infections; therefore, it may be preferred to use quantitative miracidial hatching techniques which, in addition to being more sensitive, also provide information on the viability of the eggs excreted in the feces.
• A presumptive diagnosis can be made on history and clinical signs.
• A confirmatory diagnosis can be made on the examination of fecal samples and samples from the nasal lesion which will reveal spindle-shaped egg of schistosoma.
CLINICAL SIGNS-——–
Physical examination of animals reveal sneezing, bilateral thick mucus nasal discharge, congestion of nasal mucosa
• Acute type of intestinal schistosomiasis is characterized by diarrhea; blood and mucous contained feces followed by anorexia, excessive thirst and weakness.
• The chronic type of intestinal schistosomiasis is characterized by persistent diarrhea, in some cases intermittent fetid diarrhea and feces containing blood and mucous.
• The nasal schistosomiasis is characterized by formation of granulomatous growth in the nasal mucosa resulting mucopurulent nasal discharge and partial closure of nasal passage producing snoring sound that is why it is also called snoring disease.
• Anorexia and gradual emaciation are the characteristic signs.
PATHOGENESIS
Intestinal Schistosomiasis: ——–
• Major pathological changes are caused by spiny eggs.
• Inflammatory reaction accompanied by hemorrhage in intestinal wall and other organs.
• Thickening of intestinal wall, formation of psedo-tubercules and even destruction of muscularis mucosa.
• Psedo-tubercules and pigmentation in the pancreas.
• Hydropericardium and hydrothorax are present in severe cases.
Nasal schistosomiasis: ———-
• Formation of psedo-tubercules.
• Fibrosis of nasal mucosa.
Treatment:-——–
Praziquantel (25 mg/kg) is highly effective, although two treatments 3–5 wk apart may be required. However, for practical and economic reasons, schistosomiasis in domestic stock is rarely treated. Only in China, where infected livestock constitute important reservoirs of human infection, have mass treatments with praziquantel been practiced widely.
In case of CB cows or Buffalo the treatment should be started with Inj Anthiomaline (Lithium Antimony Thiomalate) @ 15 ml intramuscularly. The cow gives response after first dose of Anthiomaline and there will be reduction in the size of nasal granuloma. The Inj Anthiomaline @ 15 ml intramuscular is repeated after weekly interval. snoring sound will be also reduced to slight sound that is audible, animal was breathing normally. Then the third injection of Anthiomaline is given after one week, The animal will show complete recovery. Anthiomaline is the drug of choice for nasal schistosomiasis .Antimony attached itself to sulphur atoms in trypanothione reductase (the putative enzyme targeted by antimonial compounds) which is used by the parasites. High incidence of schistosomiasis is seen in older animals also observed that the prevalence of Schistosoma species is high during monsoon and lowest in summer season amongst ruminants.
OTHER CHOICE OF DRUG—
Sodium antimony tartrate.
• Tatar emetic.
• Stibophen Lithium antimony thiomalate 6% solution.
• Supportive treatment with Vitamin K to arrest bleeding. In addition intestinal astringent and IV dextrose saline may be used.
Liver extract or liver stimulant should be given orally for atleast 10 days
Control:-——–
Transmission of infection occurs by percutaneous penetration of cercaria of S. nasale from the infected Indoplanorbis sp. snails. The animals should be avoided from grazing near water bodies were infected snails are noticed . Control of snails, avoiding animal grazing near snail infected areas and periodical deworming in bullocks and treatment at the early stage of infection will help in control of schistosomiasis in ruminants.
The most effective way to control cattle schistosomiasis in endemic areas is to prevent contact between the animals and the parasite by fencing of dangerous waters and supplying clean water. Unfortunately, this is not always possible in parts of the world where nomadic conditions of management prevail. Other methods of control include destruction of the snail intermediate host population at transmission sites, either by chemical or biologic methods, or their removal by mechanical barriers or snail traps. Ecologic measures against the snails that aim to render their habitat unsuitable for survival, such as drainage, removal of water weeds, and increased water flow, have also proved valuable. These measures not only help reduce the transmission of schistosomiasis but also help control other parasitic trematodes such as Fasciola gigantica and paramphistomes, which also have water snails as intermediate hosts and frequently are found in the same localities as schistosomes.
Dr.Chandrakala Sinha, Livestock consultant,Patna.
Reference:On request.
