Unit 20 srongylida monogastrics

ORDER STRONGYLIDA

  • Order belonging to the class Nematoda, subclass Secernentea.

  • Includes significant gastro-intestinal nematodes of veterinary interest.

GASTROINTESTINAL STRONGYLES OF SWINE AND BIRDS

Oesophagostomum dentatum

  • Female: Present in pigs.

  • Male: L4 stage exhibits a dorsally curved tail.

  • Hypobiotic L3 larvae can reside in the colon mucosa.

  • Size: Approximately 200μm.

  • Infections can lead to various physiological impacts on pigs.

SUPERFAMILY TRICHOSTRONGYLOIDEA

FAMILY TRICHOSTRONGYLIDAE

Genus Hyostrongylus

  • Location: Swine stomach.

  • Length: 4-12 mm.

  • Appearance: Thin, reddish, hematophagus.

  • Reproductive structure: Copulatory bursa present.

  • Hyostrongylus rubidus - Nodules containing hypobiotic L4 larvae observed in the stomach mucosa.

LIFE CYCLE OF Hyostrongylus rubidus

  • Infection is typically acquired through ingestion of L3 larvae from the environment.

  • After ingestion, L3 penetrate the stomach mucosa, where they either mature to adults or remain as hypobiotic L4 larvae.

  • Commonly found in wild boars.

SUPERFAMILY STRONGYLOIDEA

FAMILY STEPHANURIDAE

Genus Stephanurus

  • Occupies the kidney (ureters) and liver in swine.

  • Length: 20-45 mm, characterized by a large buccal capsule with a radiated crown.

LIFE CYCLE OF Stephanurus dentatus

  • Paratenic Host: Earthworms play a role in the transmission.

  • Eggs: Ellipsoidal and non-embryonated eggs found in urine.

  • Direct Life Cycle:

    • Eggs are released with urine and hatch on the ground.

    • Evolving larval forms reach L3 stage and infect the definitive host (DH) through ingestion.

    • Infection can occur by ingestion of earthworms containing L3, or L3 can penetrate through the skin.

    • Larval molts occur in the stomach or muscle leading to migration to the liver after approximately 3 months, followed by migration to the ureters; larvae may encapsulate in various organs, potentially causing obstructions.

FAMILY SYNGAMIDAE

Genus Syngamus

  • Associated with birds, specifically Syngamus trachea.

  • Size: Male smaller than female, haematophagus behavior.

  • Characterized by a buccal capsule and teeth, with eggs exhibiting mucoid plugs.

LIFE CYCLE OF Syngamus trachea

  • Direct Life Cycle:

    • Eggs are expectorated from the trachea, swallowed and then passed in feces, hatching to L3 within the egg.

    • Definitive hosts get infected by ingestion of eggs or larvae, and may also acquire infection through paratenic hosts such as earthworms or insects.

    • L3 larvae migrate via the bloodstream to the lungs, undergo development to the L4 stage in the lungs, then to the bronchi as L5.

EQUINE STRONGYLES

CLASS NEMATODA

SUBCLASS SECERNENTEA
ORDER STRONGYLIDA

SUPERFAMILY STRONGYLOIDEA

FAMILY STRONGYLIDAE

Genera:

  • Strongylus

  • Triodontophorus

  • Craterostomum

  • Oesophagodontus

  • Equine strongyles can be classified based on size:

    • Large Strongyles: >2.5 cm

    • Small Strongyles (Cyathostomins): <2.5 cm

    • Approximately 75% of the equine infections are attributed to these genera.

CHARACTERISTICS OF FAMILY STRONGYLIDAE

  • Includes both “large horse strongyles” and some “small horse strongyles”.

  • Primarily located in the large intestine (L.I.).

  • Cervical structures: Buccal capsule, which may have teeth; some species exhibit a leaf crown structure that has both internal and external crowns.

Genera within FAMILY STRONGYLIDAE

  • Genus Strongylus:

    • Species include S. equinus, S. edentatus, S. vulgaris (notably pathogenic).

    • Adults reside in the cecum and colon, exhibiting intraorganic larval migrations.

    • Morphological features:

    • Rigid worms, dark grey, averaging 2.5-5 cm in length.

    • Buccal capsule variations:

      • S. vulgaris: Forked dorsal tooth in the buccal capsule.

      • S. edentatus: Conical buccal capsule without teeth.

BIOLOGICAL CYCLE OF LARGE STRONGYLES

  • Common life cycle for species includes:

    • Eggs hatch on the ground in 1-2 days, progressing from L1 to L3 stages within 5-6 days.

    • Larval stages undergo intraorganic migration before maturing into adults found in the cecum and colon.

    • Eggs are oval with a smooth shell, expelled in a morula stage.

PATHOGENICITY

  • S. vulgaris is tracked as the most pathogenic species, necessitating a minimum of four months for larval migration through the mesenteric arterial system.

PHYSICAL CONDITIONS CAUSED BY STRONGYLUS

  • Can lead to complications such as hemorrhagic nodules and swollen blood vessels visible in abdominal surgery of horses suffering from chronic colic.

SMALL EQUINE STRONGYLES (CYATHOSTOMINS)

CHARACTERISTICS

  • Exhibit size ranging from 4-25 mm, usually found in the cecum and colon.

  • Key to note: Short buccal capsule featuring internal and external leaf crowns.

LIFE CYCLE

  • Involves a direct life cycle where L3 infective stages penetrate mucosal layers and may experience hypobiosis during colder months, forming nodules within the intestinal lining.

  • Encapsulated larvae could lead to clinical implications once they re-emerge in spring, affecting equine health.

ANCYLOSTOMID NEMATODES (HOOKWORMS)

SUPERFAMILY STRONGYLOIDEA

FAMILY ANCYLOSTOMATIDAE

Genera Include:

  • Ancylostoma

  • Uncinaria

  • Bunostomum

CHARACTERISTICS OF HOOKWORMS

  • Range in length from 6-20 mm, typically grey-reddish in color.

  • Hematophagous behavior with a deep buccal capsule; eggs resemble strongyle type eggs (approximately 8 blastomeres).

SPECIES

  • Ancylostoma caninum: Found in carnivores; largely cosmopolitan.

  • A. tubaeforme: Present in cats; widespread geographic distribution.

  • A. braziliense: Predominantly located in tropical regions amongst carnivores.

  • A. duodenale: Observed in humans, some wild animals, and swine.

LIFE CYCLE OF ANCLOSTOMID NEMATODES

  • Four affected routes of L3 include:

    1. Cutaneous Route: Larvae penetrate through hair follicles, entering the blood, traveling to the heart then lungs, leading to eventual migration to the small intestine as adults.

    2. Oral Route: Similar to cutaneous, yet initiates through the oral mucosa with the same progress as in cutaneous.

    3. Prenatal Route: Less common; larvae in muscle tissue migrate to the placenta affecting the fetus.

    4. Lactogenic Route: Larvae can migrate to mammary glands leading to infection through nursing in the first 20 days post-birth.

SIGNIFICANCE OF ANCLOSTOMID NEMATODES

  • Can lead to cutaneous larva migrans in humans and represents a public health concern due to zoonosis.

BRONCHOPULMONARY STRONGYLES

CLASS NEMATODA

SUBCLASS SECERNENTEA
ORDER STRONGYLIDA

SUPERFAMILY TRICHOSTRONGYLOIDEA

FAMILY DICTYOCAULIDAE

Genera:

  • Dictyocaulus

Characteristics

  • Large bronchopulmonary worms affecting ruminants, located in the trachea and bronchi.

  • Length: 3-10 cm, belonging to species such as D. viviparus (cattle) and D. filaria (small ruminants).

LIFE CYCLE OF Dictyocaulus

  • Adult females deposit embryonated eggs in the lungs, which are swallowed and released as L1 in feces.

  • Essential spread mechanism involves fungi (Pilobolus) aiding in L3 stage transmission.

SUPERFAMILY METASTRONGYLOIDEA

FAMILY PROTOSTRONGYLIDAE

Genera Include:

  • Protostrongylus

  • Muellerius

  • Neostrongylus

  • Cystocaulus

  • Affecting small ruminants, measuring 13-45 mm.

  • Larvae often develop within snails which serve as intermediate hosts in complex life cycles.

FINAL TRANSMISSION MECHANISM

  • Indirect Life Cycle: Host digestive process yields L1 larvae in feces, adaptable to snails and slugs creating a distinctive growth cycle, leading to potential respiratory impacts.

  • Encapsulation of lung tissue from the parasite's presence may contribute to significant health implications.

IMPORTANT SPECIES IN MEDICINE

  • Highlighted genera include Filaroides, Crenosoma, and Angiostrongylus, which can lead to serious disease pathology in both carnivorous and ruminant hosts.