Lungworm Infection in Lagomorphs

• Protostrongylus boughtoni infection
• Protostrongylus pulmonalis infection. (J1.19.w14)
• Protostrongylus sp. infection
• Synthetocaulus leporis infection

• Protostrongylus boughtoni 
  • Life cycle: 
    • Adults inhabit the bronchi of lagomorphs. (B614.11.w11)
    • Eggs hatch in the lungs and release first stage larvae. The larvae migrate in the bronchi and then are coughed up, swallowed and passed in faeces. (B614.11.w11)
    • The first stage larvae then enter the intermediate host (small land snails, e.g. Vallonia pulchella) and develop to infective third stage larvae. (B614.11.w11, J11.70.w2)
    • Third stage larvae enter lagomorphs via the ingestion of infected snails. (B614.11.w11)
  • Description: 
    • Males 13 - 26 mm long, 160 - 320 µm wide, with a copulatory bursa, and spicules 260 - 320 µm. 
    • Females 21 - 36 mm long, 160 - 250 µm wide. Vulva about 200 µm from the tail tip; the body narrows abruptly at this point.
    • Anterior end simple, lips (six) are small.
    • First stage larvae (may be found in faeces) 320 - 360 um by 14 - 16 um, with a relatively long, straight caudal appendage.

    (B614.11.w11, J11.29.w1)

  • Synthetocaulus leporis is a synonym of Protostrongylus boughtoni. (B614.11.w11, J11.29.w1)
• Protostrongylus pulmonalis (synonym Protostrongylus terminalis) in the bronchioles of rabbits and hares [species not specified] in Europe. (B24)
• Protostrongylus sylvilagi in cottontail rabbits and jackrabbits in Wyoming. (B24)
• Protostrongylus oryctolagi in rabbits in Hungary. (B24)
• Protostrongylus tauricus in hares in the USSR, central and eastern Europe and the Iberian peninsula. (B24, J210.36.w1)

• Protostrongylus boughtoni (Nematoda - Roundworms (Phylum-Division))

Clinical findings

• Bronchitis and peribronchitis have been reported associated with lungworm infection in Lepus spp. (B614.11.w11)

Pathology

• Pulmonary: 
  • Discrete, hard, yellow-grey granules can be seen in the lungs, typically in groups. (B614.11.w11)
    • Lesions are more severe in Sylvilagus floridanus - Eastern Cottontail rabbit than in Lepus americanus - Snowshoe hare. (B614.11.w11, J11.30.w1)
  • In Lepus timidus - Mountain hare and Lepus europaeus - Brown hare in Finland, affected areas were well demarcated, green and brown, mainly affecting the distal part of the caudal lung lobes. In mild cases, lesions were visible in only one lobe, while in severe cases changes were evident at the edges of all lobes. (J1.42.w5)

Histopathology:

• Adult Protostrongylus boughtoni are associated with peribronchitis and bronchitis in Lepus spp. but in Sylvilagus spp. the lesions are more severe; this may indicate that Sylvilagus spp. are abnormal hosts for this parasite. (B614.11.w11, J11.30.w1)
• In Lepus timidus - Mountain hare and Lepus europaeus - Brown hare in Finland, adult worms in bronchioles and eggs and first stage larvae in alveoli. Lesions were most severe in the caudal lobes, particularly distal areas. Bronchi were commonly blocked by a combination of the nematodes, hypertrophic epithelium, and inflammatory cells, with adjacent lung tissue necrotic and airless. In other areas, adult worms and larvae in bronchioles together with inflammatory cells (mainly eosinophils and macrophages), while no inflammatory cells were seen around eggs. Occasionally, granulomatous inflammatory reaction around a developmental worm stage, with giant cells as well as eosinophils and macrophages. Rarely, extensive lymphoid cell aggregations. (J1.42.w5)

Susceptibility/Transmission

• Transmission occurs via ingestion of infected snails. (B614.11.w11)

Diagnosis

• Detection of nematodes in the airways and lungs at necropsy. (J1.19.w14, J1.22.w10)
  • Adult worms can be seen in the airways. For detection of eggs and larvae in the lung parenchyma, areas of lung are sectioned with a scalpel and the cut surfaces scraped and examined microscopically between glass slides. (J1.22.w10)
• Histopathological examination of the lungs. (B614.11.w11)
• Isolation of larvae from faeces via the Baermann apparatus. (B614.11.w11)

Treatment

• A single dose of ivermectin (0.4 mg/kg subcutaneously (Subcutaneous Injection of Mammals)) reduced numbers of Protostrongylus boughtoni in Lepus americanus - Snowshoe hare by about 80% (at two weeks post treatment). Numbers were still reduced after four weeks, but rate of acquisition of infection was not affected after the first two weeks. (J1.32.w11) 

Occurrence

• Infection with Protostrongylus boughtoni has been reported in Lepus americanus - Snowshoe hare and Sylvilagus floridanus - Eastern Cottontail rabbit and the incidence is thought to be greater in northern regions of North America. (B614.11.w11)
  • In a cyclic population of Lepus americanus - Snowshoe hare in Alberta, Canada, prevalence of Protostrongylus boughtoni reached about 50% by the time the leverets were two months old, and remained at a similar level thereafter, although with seasonal variation (associated with larval development being arrested over winter). (J1.21.w10)
  • In a study of Lepus americanus - Snowshoe hare in southwestern Yukon, Canada, July 1990 to February 1991, Protostrongylus boughtoni were detected in 28/36 hares. (J1.32.w11)
  • In a study of Lepus americanus - Snowshoe hare at Rochester, Alberta, Canada December 1981 to April 1982, while the population was declining, prevalence in adults ranged from 38 - 64% and in juveniles from 38 - 88%. (J1.22.w10)
  • Over a four year period, lungworms (Protostrongylus boughtoni) were found in 21/50 male (42%) and 15/37 female (40%) Lepus americanus - Snowshoe hare from New York State, USA, and in 5/44 (11%) of hares from New Brunswick, Canada. (J11.29.w1)
  • In a study of the high density  Lepus americanus - Snowshoe hare on Valcour Island, Lake Champlaine, New York State, 22/22 adults (91) and 7/9 juveniles (77%) were found to be infected with Lepus americanus - Snowshoe hare; the uninfected juveniles were about four weeks old and the infected juveniles five weeks or older. The lungworms were also found in 6/7 adult and 1/3 juvenile Sylvilagus floridanus mallurus (Sylvilagus floridanus - Eastern Cottontail rabbit), which is considered an abnormal host. (J11.30.w1)
• In a study in Finland, 86.9% of Lepus timidus - Mountain hare were infected with Protostrongylus pulmonaris, as were 33.3% of Lepus europaeus - Brown hare. Infection with, and presence of visible lung lesions with, this lungworm increased with age in the Lepus timidus - Mountain hare. (J1.19.w14)
• In a study in Finland, Protostrongylys pulmonalis was found in 10/11 juvenile and 13/13 adult Lepus timidus - Mountain hare in a dense population and in 3/6 juveniles and 2/4 adults from a lower density population (1982 - 1983). (J1.28.w17)
• In a study in Finland, Protostrongylus sp. lungworms were detected in 194/201 Lepus timidus - Mountain hare (96.5%) and 18/30 Lepus europaeus - Brown hare (60%). Incidence and severity of infection was noted to increase with age, in that all individuals without infection or lesions were young hares, as were most of those with only mild lesions. (J1.42.w5)
• Protostrongylus tauricus were detected in the lungs of Lepus europaeus - Brown hare in the Northeastern Iberian Peninsula; this was noted as a new geographical record, since the parasite had previously been recorded in Central and Eastern Europe. (J210.36.w1)
• Experimental infection in a Oryctolagus cuniculus domesticus - Domestic rabbit following exposure to emerged third-stage larvae. Patent infection developed after 28 days and two male and two female adult worms were found in the lungs. (J11.70.w2)
• Protostrongylus sp. seen in 2/72 Lepus europaeus - Brown hare in Italy. (J1.27.12)
• Lungworms, probably Protostrongylus communatus in a Lepus europaeus - Brown hare in Austria. (J184.51.w1)
• Protostrongylus pulmonalis and Protostrongylus commutatus found in Lepus timidus - Mountain hare. (J469.495.w1)

• Environmental Assessment
• History & Documentation
• Physical Examination of Mammals
• Necropsy of Mammals
• Imaging in Lagomorph Diagnosis and Treatment
• Clinical Pathology of Lagomorphs
• Treatment and Care
• Environmental and Population Management
• Preventative Medicine for Mammals
• Chapter 2 - B36 Field Manual of Wildlife Diseases - Specimen Collection and Preservation
• Chapter 3 - B36 Field Manual of Wildlife Diseases - Specimen shipment
• Appendix A - B36 Field Manual of Wildlife Diseases - Sample specimen history form
• Subcutaneous Injection of Mammals

• Lepus americanus - Snowshoe hare
• Lepus europaeus - Brown hare
• Lepus timidus - Mountain hare
• Oryctolagus cuniculus domesticus - Domestic rabbit [Experimental infection]
• Sylvilagus floridanus - Eastern Cottontail rabbit