Laboratory 10

INSECTS OF VETERINARY IMPORTANCE

    

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Card 10:1

      Simulium spp. "Black Fly"

      Eggs

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Card 10:2

      Simulium spp.

      A) Under the microscope is an early larval stage.

      1) It is cylindrical
      2) It has a posterior sucker-like organ armed with hooks. It is used as a holdfast to anchor the larva in fast moving streams.
      3) It has an anterior pair of mouth brushes.
      4) The ventral proleg is armed with hooks on its anterior end. It is used to migrate in "inchworm" fashion.

      B) Compare the size of this early larval stage with a later larval stage in the dish next to the microscope.

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Card 10:3

      Simulium spp.

      PUPA

      A) It is enclosed in a cocoon which is spun by the salivary glands of the last larval stage.

      B) It is an exarate pupa, that is, it is not covered by the 3rd larval skin. (eg. Simulium, Tabanus, Culicoides). A pupa covered by the hardened 3rd larval skin is known as a coarctate pupa. (eg. Cyclorrhapa).

      C) It has respiratory filaments on the anterior end.

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Card 10:4

      Simulium spp.
      A) The humpbacked appearance.
      B) The multisegmeted antennae.
      C) Short proboscis.
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Card 10:5

      Tabanus

      Wing veins are important in identifying flies; however, you are not responsible for knowing the different wing vein patterns. But you should know the antenna types.

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Card 10:6

      Tabanus spp.

      LARVA

      Note the fleshy tubercles on each segment.

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Card 10:7

      Gasterophilus intestinalis and              G. nasalis

      Distinguish between the larvae using the key provided (figure #5 in lab book).

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Card 10:8

      Gasterophilus intestinalis

      Larvae attached to the mucosa of the stomach of a horse. You can see lesions where the larvae have detached. Note the rings of inflammatory thickening with eroded centers where the larvae were attached.

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Card 10:9

      Gasterophilus sp.

      Left: egg on the hair of a horse leg. Right: bottle filled with horse hairs and attached eggs.

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Card 10:10

      Gasterophilus sp.

      Adult

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Card 10:12

      Lucilia, Sarcophaga, and Calliphora adults

      See lab handout.

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Card 10:13

      Wing veins are important in identifying flies; however, you are not responsible for knowing the different wing vein patterns. But you should know the antenna types. .

                                                                         

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Card 9.13A

Cyclorrhapha:

Fly head (enface)

Note the typical club-shaped

antennae laying in the groove

between the eyes.

 

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Card 10:14

      Oestris ovis larvae - sheep nasal bot

      These were removed from the nasal cavities and frontal sinuses of sheep at New Bolton Center on post-mortem examination at the beginning of March.

      Note:

      1. Shape and size
      2. Large black oral hooks
      3. Posterior spiracles
      4. Morphology of spiracular plate
      5. Bands of spines on the ventral surface
      6. As the larvae matures it develops the brown bands on the dorsal surface of its segments.

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Card 10:15

      Cuterebra larva

      This is a mature larva which would be found in a dermal pocket in the host. Note:

      1. The dark color of the mature larva.
      2. The larva is covered with spines.
      3. Morphology of spiracular plate.
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Card 10:16

      Leather damage due to Hypoderma

      This piece of leather shows the lesions following the emergence of Hypoderma sp. larvae from the back of a bovine. When the lesions heal, light spots which are scars form. The scars lower the price received for the hide.

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Card 10:17

      Hypoderma sp. - Mature larvae
      H. bovis
      28 mm
      Barrel shaped
      Spiracle plates ear shaped, surface depressed, opening narrow, spiracle button small.
      Ventral surface of penultimate segment unarmed.
      		 H. lineatum
      25 mm
      Thinner, more pointed at ends
      Spiracle plates kidney-shaped. Surface level, opening wide, spiracle button well defined.
      Ventral surface of penultimate segment armed with spines

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Card 10:18

      Melophagus ovinus - sheep ked

      (Fam: Hippoboscidae)

      Collected from lambs at New Bolton Center

      Note:

      1. This is a wingless fly (order: Diptera).
      2. Strong legs
      3. Sac-like abdomen

      The adults live in the wool of sheep. The female lays mature larvae and cements them to the wool. The larvae immediately pupate. The adults irritate sheep by their bites and soil the fleece with feces and blood. Wool is damaged when the sheep scratch and rub themselves.

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Card 10:19

      Flea Life-Cycle

      Egg - larva - pupa - adult

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Card 10:20

      Ctenocephalides felis - larvae

      These larvae are free-living. Live larvae may have a red color from feeding on the adult flea's feces and dried blood. Note the tuft of strong bristles at the posterior end.

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Card 10:21

      Ctenocephalides felis - the cat flea

      The cat flea, the dog flea, and the human flea can act as intermediate hosts for Dipylidium caninum. The larval stage of the flea becomes infected eating D. caninum eggs, and cystercercoids then develop within the flea. The final host (dogs, cats, man) acquire the infection by swallowing the infected adult flea.

      Note:

      1. The head is longer (less blunt) than that of the dog flea, C. canis.

      2. The first two spines on the genal ctenidium are almost the same size.

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Card 10:22

      Ctenocephalides canis

      Note: General structure - head, thorax, abdomen and 3 pairs of legs.

      Presence of both genal and pronotal ctenidia (combs). Short first tooth on the genal ctenidium. The head is more rounded than that of C. felis.

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Card 10:23

      Trichodectes canis- biting louse of dogs

      Note: General structure

      - Head, thorax, abdomen dorsoventrally flattened
      -Three pairs of legs with 1 claw at the end of each leg
      - Antennae extend laterally from head (Suborder Ischnocera)
      - Head: anterior end is broad and flat: characteristic of the biting lice
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Card 10:24

      Damalinia caprae

      Adult on goat hair

      This louse belongs to the suborder Ischnocera (see the characteristics of Trichodectes canis).

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Card 10:25

      Linognathus setosus - Nit (egg)

      Egg glued to the hair of a dog.

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Card 10:26

      Linognathus sp.

      Sucking lice of this genus are found on cattle, goats, sheep and dog.

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Card 10:27

      Haematopinus spp. - sucking louse

      Note: General structure

      - Head, thorax, abdomen dorsoventrally flattened
      - Three pairs of strong legs each with a claw
      - Antennae extend laterally from head - 5 segments

      - Narrow, pointed head with recessed stylets (adapted for sucking).

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Card 10:28

      Phthirus pubis - crab or pubic louse of humans

      - a sucking louse (Anoplura).

      Note:

      1. Head bearing antennae
      2. Thorax with 3 pairs of legs. (The first pair of legs is slender compared to the others.)
      3. Broad abdomen.
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Card 10:29

      Pediculus humanis head or body louse of humans

      - a sucking louse (Anoplura)

      Note:

      1. The body is longer than that of Phthirus pubis.
      2. Head bearing antennae
      3. Thorax with 3 pairs of legs
      4. Oval abdomen

      The nymphs are smaller but have a very similar structure to the adults.

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Card 10:30

      Review Question

      This louse was removed from a dog that had tapeworm segments in its feces.

      A. Identify the louse (be specific as possible).

      B. Could the dog have gotten the tapeworm from this louse?

      Click here for answer

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