Overview

Brief Summary

History of Identifcation

] The first major studies on Histoplasma were not conducted until the early twentieth century and were confined to research on the human infecting variety Histoplasma capsulatum. In 1903 Doctor Samuel Taylor Darling was sent down to Panama to address new relevant diseases that were appearing within the Panama Canal worker populations.[6] Samples were taken from patients and identified at the microscopic level. Blood smears showed halo shaped figures invading the blood which Darling falsely claimed to be a protozoan variety of parasite.[9] Several years later in 1912 a Brazilian pathologists Henrique da Rocha-Lima correctly identified the parasite to be a variety of fungus.[6] He was able to correctly identify the equine variety where the species was correctly renamed to Histoplasma capsulatum var. farciminosum (Hisstoplasma farciminosum for short). Further phylogenetic research was concluded following da Rocha-Lima’s research to factually identify this species for its official name change in 1985.[6]

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Summary

Histoplasma farciminosum is a parasitic fungi more commonly known as the precursor for equine species to contract epizootic lymphangitis.[10] This fungus has been tormenting equine species namely horses, donkeys, and goats in undeveloped and developing countries for centuries.[2] The disease was never officially identified at any point in time due to how spread out the disease is as well as the misidentification for generations and common name confusion. Unfortunately the side effects of the fungus resemble a variety of different diseases including malaria in humans.[6] 

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Distribution

Continuation of Disease

Ethiopia is one of the most impacted countries from Histoplasma farciminosum spanning the whole country and spreading continuously.[9] This contagious disease is spread through markets where animals interact and then travel to different locations where the spores can relocate for new infestations. It does not compete with any other species of fungi for its host making this disease highly deadly. As recorded in 2006 Ethiopia ranks epizootic lymphangitis second behind only African horse sickness as the most impactful horse diseases in the country.[3] Other countries have been much more successful at eradicating the disease including Great Britain which was able to do so by 1906 through direct slaughter once the disease was identified.[8] Epizootic lymphangitis has slowly been contained to a number of areas and countries, but in much poorer countries where citizens rely on their equine species for survival the end to this disease does not seem to be coming near.

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Effected Locations

Histoplasma farciminosum is endemic to many places across the world including Ethiopia, India, the Middle East, Northern Africa, and many other locations.[8] It sustains itself in areas between 1600 to 2400 meters above sea level where rainfall is common and it is warm all year round.[4] These seem to be the most adequate conditions for this fungus to survive and spread readily.

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Physical Description

Morphology

General Physical Identifiers

Histoplasma farciminosum is a fairly common causer of disease in equine species within developing countries where large populations of horses and donkeys interact on a regular basis. The dimorphic fungi goes unnoticed until it invades its host where it is much easier to identify.[8] Once H. farciminosum invades its host it produces lesions filled with pus which can be extracted and examined for its spore presence. The spores are said to look like they have a halo around them and very closely resemble yeast.[9] The other phase in its life cycle reveals more of its relationship with other fungi due to its presence of a saprophytic mycelial network in soils.[1] Histoplasma farciminosum also has septate hyphae making up its mycelial network which can be further used as a tool for identification.[4] Due to this dimorphic life cycle H. farciminosum has a large number of opportunities to continue to spread to new hosts. This fungus does not have a distinctive characteristic that stands out amongst other fungi, but it specifically only targets equine species and produces routine side effects.

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Diagnostic Description

Equine Disease

Equine species are very susceptible to becoming hurt or sick from a number of causes and Histoplasma farciminosum is just one more thing added to the list. In developing countries horses and donkeys are used not only for transportation but also for working purposes to make a livelihood. This fungus targets mainly horses, mules, and donkeys but other close relatives including camels and cattle have been previously reported.[2] It feeds off the tissues of the animals internally as well as externally once it enters the system through either open sores, breathing the spores in, or bugs spreading the spores to the hosts. 

Although Histoplasma farciminosum is most commonly known and recognized for its parasitic portion of its life it is surprisingly only part of its life story. Histoplasma farciminosum is unique in the fact that it has not only a parastitic portion to its life but also a saprophytic portion during its larger growth form.[8] It receives energy directly through the tissues of its host or retrieves its nutrients from decomposing materials. When invading the tissues of equine species the disease it causes is referred to as Epizootic Lymphangitis, which is highly contagious amongst populations and puts high risk to a large number of animals.[10] Most infected animals in current endemic countries tend to be worked while they are infected furthering the spread of the disease. As H. farciminosum persists the equine species eventually cannot fight the disease and are left to die on a regular basis.[2]

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Conservation

Management

Economic Impact

Developing countries have to deal with a lot of stress on a daily basis usually surrounded around basic survival. One problem within the hot moist countries has come from the disease epizootic lymphangitis caused by Histoplasma farciminosum. This equine killer has infested thousands of animals with little to no competition. Although veterinary clinics are attempting to disperse antibiotics to people in their countries they are finding that not all animals will respond to the experimental drugs.[2] The prices are just too high for these drugs and the risk and reward is not worth it to most handlers on very strict budgets. A study done back in 1985 was able to conclude that on average every case of epizootic lymphangitis caused a net loss of $1,683 US dollars.[3] This extraneous amount can hurt families in countries like Ethiopia where equine species are the main form of transportation as well as a form of work.

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Notes

References

[1]Al-Ani, F. K. (1999) Epizootic lymphangitis in horses: a review of the literature. Revue

 Scientifique et Technique – Office International des Epizooties 18, 691-699

[2]Ameni, Gobena. 2006. "Epidemiology of equine histoplasmosis (epizootic lymphangitis) in

            carthorses in Ethiopia." Veterinary Journal 172, no. 1: 160-165. Academic Search

            Premier, EBSCOhost (accessed October 22, 2017).

[3]Ameni, Gobena. 2006. "Preliminary trial on the reproducibility of epizootic lymphangitis

            through experimental infection of two horses." Veterinary Journal 172, no. 3: 553-

            555. Academic Search Premier, EBSCOhost (accessed October 21, 2017).

[4]Ameni, G, Terefe, W, & Hailu, A 2006, 'Histofarcin test for the diagnosis of epizootic

            lymphangitis in Ethiopia: development, optimisation, and validation in the

            field', Veterinary Journal, vol. 171, no. 2, pp. 358-362. Available from:

            10.1016/j.tvjl.2004.10.017. [21 October 2017].

[5]. Gurein, S. Abebe, F. TouatiLymphangite epizootique du cheval en Ethiopie Journal of

           Mycological Medicine, 2 (1992), pp. 1-5

[6]Hagan, Teresa. “The Discovery and Naming of Histoplasmosis: Samuel Taylor Darling.”

          Antimicrobe, accessed October 23, 2017.

[7]Inglis, R. (1997) Ocular disease of the donkey. In The Professional Handbook of the Donkey.

 3rd edn. Ed E. D. Svendsen. London, Whittet Books. pp 37- 42

[8]Jones, Karen. 2006. "Epizootic lymphangitis: The impact on subsistence economies and animal

 welfare." Veterinary Journal 172, no. 3: 402-404. Academic Search Premier,

 EBSCOhost (accessed October 22, 2017).

[9]Powell, R. K., N. J. Bell, T. Abreha, K. Asmamaw, H. Bekelle, T. Dawit, K. Itsay, and G. A.

 Feseha. 2006. "Cutaneous histoplasmosis in 13 Ethiopian donkeys." Veterinary Record:

Journal Of The British Veterinary Association 158, no. 24: 836-837. Academic Search

Premier, EBSCOhost (accessed October 21, 2017).

[10]R.J. Weeks, A.A. Padhye, L. AjelloHistoplasma capsulatum variety farciminosum: a new 

                              combination for Histoplasma farciminosum Mycologia, 77 (1985), pp. 964-970

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