Exercise 35. Match symptoms with the disease.

Demodicosis	change of voice; weakness of back legs (later – wobbliness of back legs); vomiting; excessive salivation; panting, loud breathing; moist cough; animal is unable to stand; gums are cold and blue-tinged; death comes from respiratory paralysis
Tick paralysis	tapping the muzzles on the ground; snorting and stamping the front feet in annoyance; irritation to the mucosa; mucous discharge; swelling of the internal membranes of the nose; malfunction of breathing and large discomfort; no grazing; weight and condition losses; malnutrition
Oestrosis	disease affects animal’s muzzle, trunk, or legs; thinning hair, scaly skin, and the skin itself will appear reddish-brown; or skin lesions are more widespread and may involve the entire body; scruffy appearance; hair loss; discoloration of the skin; poor appetite; nodules and papules

 

 

UNIT 8

HELMINTHS

TEXT A

PARASITIC WORMS

VOCABULARY LIST TO TEXT A

alimentary adj	[ælɪˈmentərɪ]	пищеварительный
burrow v	[ˈbʌrəʊ]	внедряться, прятаться
cestode n	[ˈsesˌtǝud]	цестода
competitor n	[kəmˈpetɪtər]	конкурент
definite adj	[ˈdefɪnət]	окончательный
feces n	[ˈfiːsiːz]	фекалии
fluke n	[fluːk]	сосальщик
hatch v	[hætʃ]	вылупляться, выводиться
helminth n	[ˈhelmɪnθ]	гельминт
helminthiasis n	[ˌhelmɪnθˈaɪǝsǝs]	гельминтоз
hermaphrodite n	[hɜːˈmæfrədaɪt]	гермафродит
hook n	[hʊk]	крючок
impaired adj	[ɪmˈpeəd]	ослабленный, ухудшенный
insufficient adj	[ˌɪnsəˈfɪʃənt]	недостаточный
intermediate adj	[ˌɪntəˈmiːdiət]	промежуточный
larva (larvae) n	[ˈla:vǝ]	личинка
metamorphosis n	[ˌmetəˈmɔːfəsɪs]	метаморфоза, превращение
molt n	[məʊlt]	линька
nemathelminth n	[ˌnemǝˈθelmɪnθ]	нематогельминт, круглыйчервь
nematode n	[ˈnemǝˌtǝud]	нематода
obligate adj	[ˈɔblɪgeɪt]	облигатный, обязательный
phylum(phyla) n	[ˈfailəm]	тип, филум
platyhelminth n	[ˌplatiˈhelmɪnθ]	платигельминт,плоский червь
proglottid n	[proˈgloutǝd]	проглоттид
scolex n	[ˈskouleks]	сколекс (головная часть)
sewage n	[ˈsuːɪdʒ]	сточные воды
sucker n	[ˈsʌkər]	присоска
tapeworm n	[ˈteɪpwɜːm]	ленточный червь
trematode n	[ˈtremǝˌtǝud]	трематода

 

Helminths, also known as parasitic worms, are multicellular eukaryotic invertebrates, which live in the gastrointestinal tract of their host, or may burrow into other organs, such as lungs, heart, kidneys, liver. Helminths important in veterinary medicine are classified into two phyla: Platyhelminthes and Nemathelminthes. The first group is commonly known as flatworms and is subdivided into cestodes or tapeworms and trematodes or flukes. Nemathelminthes has only one class named nematodes or roundworms.

Cestodeshavetape-like, flattened, segmented bodies. Anatomically, they are divided into a scolex, or head, carrying suckers and/or hooks,a neck and a chain of segments called proglottids. They vary in length from 2 to 3 mm to 10 m, and may have three to several thousand segments.Cestodes lack alimentary system, and nutrients are absorbed through the body covering. Body cavity is absent. Tapeworms are hermaphroditic,it means that they have both male and female reproductive organs in the same individual. The adults of most species live only in the intestinal tract of their hosts.

Trematodes are leaf-shaped, unsegmented worms, ranging in length from a few millimeters to 7 to 8 cm. All of them have an oral sucker around the mouth, and another on their ventral surface. They possess an alimentary canal, but it is incomplete. Except for the blood flukes, trematodes are hermaphroditic. Adults of most trematodes live in the gastro-intestinal system, including the liver, gall bladder and bile ducts. Other species parasitize the lungs, the vascular system or the urinary tract.

In contrast to platyhelminths, nematodes are cylindrical rather than flattened, and vary with species from a few mm to more than 50 cm in length. They possess a relatively well-developed complete alimentary canal, with mouth surrounded by lips and armed with teeth or cutting plates, and anus. Most nematode species form two separate sexes, with male and female individuals, males are usually smaller than females. Roundworms may inhabit not only intestinal tract, but also the heart, arteries, lungs.

Nematodecestodetrematode

All parasitic worms are obligate parasites, which means that they cannot complete their life cycle without spending some time on their host. The life cycles of helminths are either direct or indirect. The worms with direct life cycles reach maturity and reproduce in a single host that is called definite or final host. Many nematodes have direct life cycles. Typical for flukes and tapeworms indirect life cycles require one or more intermediate hosts in addition to the definite host. Inside these intermediate hosts, the worms complete certain development stages and may reproduce asexually.

In general, helminths exist in three morphological forms – 1) eggs, 2) larval form and 3) adult form (or the worm).Adult worms reach sexual maturity and reproduce inside their host and produce thousands (some species millions) of eggs that are expelled mostly through the feces. Eggs have a strong shell that protects them and let them remain viable for months in soil, fresh water or sewage, and even for years in feces. Larvae hatch out of these eggs and undergo several metamorphoses (molts) depending on the species. The duration of each development stage vary with ecologic and climatic conditions. Knowledge of the life cycle is very important for establishingand managing preventive measures.

Some parasitic worms are host specific, it means that they can complete development only on that particular host species or closely related ones. If infective larvae get into an unsuited host, they will mostly die without causing any harm. But some worm species can be very harmful for such non-final hosts, also calledfacultative or transporthosts. Typical facultative hosts are small vertebrates such as frogs, lizards, rodents, squirrels. The final hosts get infected by ingestion these facultative hosts.

The signs and symptoms of worm infection, which is known as helminthiasis, depend on a number of factors, including the site of the infestation within the body, the type of worms and the number of them, the immunological response of the animal involved. Some parasitic worms are live threatening for livestock and pets, other species are well tolerated by their hosts without apparent damage. Often helminths are competitors for food, which is virtually "stolen" by the worms living in the host's digestive system. This causes significant productivity losses in livestock: weight loss, insufficient growth, reduced milk or egg production, impaired fertility.Well-nourished, healthy animals often tolerate considerable worm numbers without developing a disease.

 

EXERCISES TO THE TEXT