CASE IV:
Signalment:
1-year-old male Gould finch (Erythrura gouldiae)
History:
The patient suffered for a long time from chronic respiratory disease, characterized by coughing, respiratory distress mostly evident during physical activity and environmental stress. The patient was found suddenly dead in the cage by the owner.
Gross Pathology:
The finch was severely cachectic. The air sacs were severely thickened, opaque and whitish. The lungs appeared severely congested and multifocally fleshy and firm.
Laboratory Results:
None Available
Microscopic Description:
Section of lung and air sac.
Lung is diffusely characterized by hyperemia of alveolar capillaries and bronchial vessels. Multifocally in the lumina of bronchi, alveoli and on the surface of air sacs several mites are evident. Mites are characterized by chitinous exoskeleton, joint appendages, thick muscular layer, intestine with lumen occasionally containing red blood cells and reproductive tract with numerous eggs (arthropods consistent with Sternostoma tracheacolum).
Mites are often surrounded by rows of granular macrophages admixed with foreign-body giant multinucleated cells and lesser number of lymphocyte and plasma cells.
Contributor's Morphologic Diagnoses:
Lung MD: severe, multifocal, chronic, granulomatous bronchopneumonia and aerosacculi-tis with intralesional arthropods consistent with Sternostoma tracheacolum.
ND: Respiratory acariasis
Contributor's Comment:
Mites of the family Rhinonyssidae Trouessart, 1895, popularly known as nasal mites, are obligatory endoparasites of birds that specifically target the respiratory system1. This family is organized in eight genera, including about 500 species, and has been described around the world. Sternostoma represents one of the genera belonging to the family Rhinonyssidae. Sternostoma tracheacolum Lawrence, 1948 is spread worldwide and has been recorded in both captive and wild birds. Sternostoma tracheacolum has been described for the first time in captive canaries (S. canarius) by R. F. Lawrence in 1947 in South Africa. This species resides throughout the respiratory system, ranging from the trachea to the air sacs, and is known to cause complications. In particular, Sternostoma tracheacolum is the only species of mite from the family Rhinonyssidae that is capable of infecting not only the nasal passages of birds but also the tracheae, lungs and air sacs, causing serious respiratory problems2. The most common clinical signs are dyspnea, coughing, sneezing, and in severe infestations the host may die from asphyxiation or due to severe pneumonia and inflammation of air system3.
Sternostoma tracheacolum is a generalist parasite infecting many species of hosts. In a large-scale survey involving 103 species and 502 individual birds, the author found the parasite in 40 species and in 87 birds with a prevalence of 17%3.
High prevalence of Sternostoma tracheacolum was found also in house sparrow (Passer domesticus)2. The broad geographic distribution of Passer domesticus and its adaptability to different ecosystems around the world including urban and rural areas, make Passer domesticus an important reservoir for a number of pathogens of interest and concern for public and animal health, including Sternostoma tracheacolum2.
Tidemann et al. (1992)24 documented the occurrence of Sternostoma tracheacolum in wild passerines in Australia where the prevalence of this mite infection was 62% in the Gouldian finch, Erythrura gouldiae (Gould, 1844). The authors reported that Erythrura gouldiae had 34.1 mites/bird (1-102 mites); mites were found in different anatomical locations. The authors suggested that Erythrura gouldiae has not been able to regain its former population status due to Sternostoma tracheacolum infection. According to the IUCN Red List of Threatened Species, the Gouldian finch has been endangered since the 1980s2.
Contributing Institution:
San Marco Veterinary Clinic and Laboratory Pathology division
Viale dell'Industria 3, 35030 Veggiano (PD), Italy
https://www.clinicaveterinariasanmarco.it/
JPC Diagnoses:
Lung: Bronchopneumonia, granulomatous, chronic, multifocal to coalescing, moderate with adult mites and mild granulomatous and proliferative airsacculitis.
Bone marrow: Fat atrophy, chronic, diffuse, severe.
Skeletal muscle: Myocyte atrophy, chronic, diffuse, severe.
JPC Comment:
First things first... How did this brightly colored bird get its name? The bird, a colorful passerine within the ranks of Australian fauna, was named by British ornithologist Sir John Gould from several specimens he received from British naturalist Benjamin Bynoe. Although this species had been described years prior by French naturalists Jacque Bernard Hombron and Honore Jacquinot. Ignoring that pesky fact, Sir John Gould named the finch Amadina gouldiae after his dead wife Elizabeth. The genus Amadina is a related genus of parrotfinches, and the species has also spent time in the genera Chloebia and Erythrura. It also goes by a range of given names, with the rainbow finch describing its colorful plumage, the Gouldian finch, and the Lady Gouldian finch.
The contributor has provided an excellent review of the rhynonyssid or nasal mites of finches and related species, to include Sternatstoma tracheocolum, but perhaps a brief review of other nasal and respiratory mites are in order.
Staying with avian species, the air sac mite is a common parasite of a wide range of poultry, including chickens, turkeys, gamebirds, canaries and pigeons. These mites result in air sac disease, and light infections are well-tolerated, but heavier infections result in granulomatous inflammation of the airways, lungs, and pneumatic bones.
Respiratory mites are not unheard of in mammalian species as well. Orthohalarachne (which infects sea lions and walruses) and Halarachne sp. (which infect seals and sea otters), which have piercing mouthparts can cause significant irritation, and may transmit bacterial pathogens such as Streptococcus phocae as well. How this occurs is not yet clear. It may simply pierce the respiratory mucosa with their mouthparts, may diminish the immune system in affected animals, or it could represent a true host/vector/pathogen relationship.
A few more well-known mites parasitize dogs and non-human primates. Pneumonyssoides caninum, a global parasite that appears concentrated in Scandinavia. Presence of this mite results in sneezing (both conventional and reverse, nasal pruritus, serous discharge, anosmia, and epistaxis, and aberrant migration may result in lacrimation, orbital cellulitis, and nervous signs. The mite has even once been suggested to be a cause of gastric dilation-volvulus due to aerophagia associated with reverse sneezing.8
Finally, one of the most well-known respiratory mites known to pathologists and laboratory animal medical practitioners is Pneuonyssus simicola, the air sac mite of non-human primates. These mites are seen with a frequency of almost 100% in wild and wild-caught Old World primates. Histologic findings include granulomatous to eosinophilic bronchitis and bronchiolitis due to the presence of mites and their excreta. Over time, the presence of the mites, their golden-brown iron-laden excreta, and the inflammation that all of this creates results in bronchiectasis, and the formation of what is known as colloquially referred to "mite houses" in the lungs of affected macaques.
References:
- Bassini-Silva R, Jacinavicius FC, Pereira JS, Werther K, Spicer GS, Barros-Battesti DM. Parasitism of the nasal mite Sternostoma tracheacolum Lawrence, 1948 (Mesostigmata: Rhinonyssidae) in captive birds in Brazil. Rev Bras Parasitol Vet. 2019 Oct-Dec;28(4):754-759.
- Santos LSSD, Mascarenhas CS, Santos PRSD, Farias NADR. Rhinonyssidae (Acari) in the house sparrows, Passer do-mesticus (Linnaeus, 1758) (Passer-iformes: Passeridae), from southern Brazil. Rev Bras Parasitol Vet. 2018 Oct-Dec;27(4):597-603.
- Spicer GS. Prevalence and host-parasite list of some nasal mites from birds (Acarina, Rhinonyssidae, Speleognathidae). J Parasitol 1987; 73(2): 259-264.
- Tidemann SC, McOrist S, Woinarski JCZ, Freeland WJ. Parasitism of wild Gouldian finches (Erythrura gouldiae) by the air-sac mite Sternostoma tracheacolum. J Wildl Dis 1992; 28(1): 80-84.
- Ayroud M, Dies KH. Cytodites nudus-induced granulomatous pneumonia in chickens. Can Vet J. 1992 Nov;33(11):754-5. PMID: 17424122; PMCID: PMC1481428.
- Pesapane R, Chaves A, Foley J, Javeed N, Barnum S, Greenwald K, Dodd E, Fontaine C, Duignan P, Murray M, Miller M. Nasopulmonary mites (Acari: Halarachnidae) as potential vectors of bacterial pathogens, including Strepto-coccus phocae, in marine mammals.
- Wills, S.J., Arrese, M., Torrance, A., Lloyd, S., Pratschke, K., Whitbread, T. and Gould, S. (2008), Pneumonyssoides species infestation in two Pekingese dogs in the UK. Journal of Small Animal Practice, 49: 107-109. https://doi.org/10.1111/j.1748-5827.2007.00500.x
- Bredal WP. Pneumonyssoides caninum infection--a risk factor for gastric dilata-tion-volvulus in dogs. Vet Res Commun. 1998 Jun;22(4):225-31.