Exam 2 - Lecture 15 Flashcards
Lecture 15
Nematode Parasites of the Respiratory System
-General Morphology & Biology
-Small worms with superficial resemblance to hookworms:
-Dioecious & sexually dimorphic
-Males with rudimentary copulatory bursa
-Occupy respiratory tract and pulmonary vasculature
-Generally, feed on host cellular tissue
-Companion and Production Animals
-Most develop to infective stage in obligate intermediate host
-Some exceptions!
Dog Lungworms - (Metastrongyloidea) - -Filaroides hirthi
-Adult worms are parasitic in the lung parenchyma
-Prepatent period ~ 35 days (5 wks)
Dog Lungworms - (Metastrongyloidea) -Filaroides osleri
-Adult worms are parasitic in nodules in the trachea and bronchi
-Nodules detected by bronchioscope @ 2 months
-Prepatent period ~ 6 to 7 months
Filaroides spp. - Life Cycle Biology
-Direct Life Cycle:
-1st stage larvae ( L1) passed in the feces of infected mother
-Ovoviviparous: eggs hatch w/in uterus of
adult female worms
-Puppies infected by ingestion of the L1
through:
-Coprophagy
-Ingestion of larvae in regurgitated stomach contents
-Transmission pathway adapted from wild canid behavior?
-Tracheal migration by the hepatic circulation
-Prepatent period ~32 days post‐infection (F. hirthi)
-Prepatent period 6 ‐7 months post‐infection (F. osleri)
**This is the only nematode where the 1st larval stage is infective tothe final host
Filaroides spp. - Diagnosis
-Diagnosis by fecal examination:
-Baermann exam
-Zinc Sulfate flotation
-Successive daily collection enhance sensitivity of diagnosis
-Larvae ~ 350μm:
-Kinked tail w/ dorsal spine
Baermann Exam Technique
-Developed in 1917 by Dutch
-Physician working in Java for recovery of hookworm larvae in soil samples
-Preferential for recovery of live larvae in fecal samples & cultures
-Active migration of larvae out of fecal sample suspended in water
-Larvae concentrate in stem by gravity
-Microscopic wet mount by pipetting larvae from bottom of stem
Filaroides spp. - Clinical Significance
-Generally asymptomatic
-Clinical signs may include hard, dry coughing
-Stimulated by cold air or exercise
-Chronic & unremarkable
-Pathology seen as focal areas of inflammation & necrosis in the parenchyma of the lung lobes
-Possible obstruction of trachea with nodular formation in hyper‐infections
-Severe disease in hyper infected & immunocompromised animals
Filaroides spp. - Treatment and Prevention
-Treatment is difficult with variable results
-Criteria for efficacious chemotherapy:
-Clinical improvement, cessation of symptoms
-Resolution of nodular lesions (bronchoscopy)
-Cessation of larval shedding
-FBZ @ 50mg/kg SID for 7 days resolved symptoms:
-FBZ @ 50mg/kg SID for 14 days failed to remove worms
-IVM @ 1000μg/kg (x1) or (x2) was 44% & 74% effective (Filaroides hirthi @ necropsy):
-5 to 10% of treated dogs continued to shed larvae
-Higher % of treated dogs w/ worms in tissues, but fecal negative
-Prevention by avoiding contact w/ infective larvae; easier said than done!
Angiostrongylus vasorum - French Heartworm
-Small worms living in the right heart/ pulmonary artery
-Widespread in Europe, thought to be a recent introduction to North America (~1998 1st case)
-Associated with pulmonary thrombosis, clotting disorders, hemorrhage from deposited eggs &
larvae
-Successfully treated w/ .5 mg/kg Milbemycin weekly (x4) * Standard monthly Heartworm prophylactic dose
-Other treatment regimes described in Bowman, pp 188
-NOT ZOONOTIC
Angiostrongylids in North American Wildlife
-Incidental finding in a necropsied Red Fox (Vulpes vulpes) from West Virginia
-Putative diagnosis based on larvae in observed on histopath:
-Nonspecific morphology of larvae among shared species and genera in family
-Closely related species (Angiocaulus gubernaculatus) had a significant distribution in Channel Island fox (Urocyon littoralis):
-Did not seem to be associated with significant pathology
-Parasite was eradicated with successful treatment w/ Ivermectin
Angiostrongylus costaricensis - Zoonotic Significance
-Associated with abdominal pain, fever, vomiting from worms living in mesenteric arteries
-Endemic to Central & South America and Caribbean
-Spread in Florida associated w/ deaths in primate colonies: Raccoons & Opossums trapped near zoo also infected
-Spread to Africa w/ Cuban mercenaries in Angola in 1980’s
Angiostrongylus cantonensis - Zoonotic Significance
-Associated with neurologic disease from larvae in the meninges and inflammatory response
-Naturally occurring in rats in Southeast Asia:
-Spread with distribution of giant African Snail
-Associated with canine neurologic disease in Australia
-Spread to North America 1986‐87 (New Orleans) in wharf rats from Asia:
-Fatal case in Howler monkey in New Orleans Zoo
-25% prevalence in Baton Rouge rats
-Other captive primates (gibbon, lemur, Old World monkey)
-1st human case (1995)
Angiostrongylus cantonensis: An important Emerging Zoonosis & One Health Issue
-Most recent issue from Jour Emerging Infect Disease
-Autochthonous case:
-Native acquired, indigenous
-Well established zoonosis throughout the Fla‐Gulf Coast states:
-Colonized non‐native snails from Asia & Caribbean
-Indigenous native snails
-Additional infant cases recently reported from Houston TX
-Combination treatment ABZ w/ corticosteroids vs. corticosteroids alone not significantly different
Aleurostrongylus abstrusus - (Cat Lungworm)
-Lifecycle is indirect:
-1st stage larvae passed in feces ingested by snail/ slug intermediate host
-L3 is the infective stage
-Mice/birds opportunistic paratenic hosts
-“Bridging the ecologic gap”
-Prepatent period 5 to 6 weeks
Aleurostrongylus abstrusus - Pathogenesis
-Tiny adult worms are parasitic in the terminal bronchioles and alveolar ducts,
-Eggs are laid in lung parenchyma
-“nests” of worms appear as small nodules w/ associated inflammatory response and focal necrosis
