Diagnosing a rare human disease in Mexico’s lowlands

Diagnosing a rare human disease in Mexico’s lowlands

Diagnosing a rare human disease in Mexico’s lowlands

The first multidisciplinary study using DNA barcodes as a medical diagnostic tool forms a unique collaborative group comprised of medical practitioners and scientists.

Scanning electron micrograph of the anterior part of Lagochilascaris minor.
PHOTO CREDIT: Manuel Elías-Gutiérrez

Roundworms (Nematoda) are one of the most diverse groups of invertebrates. Lagochilascaris minor, a parasitic nematode often found in wild cats such as jaguars and pumas, as well as in domestic cats and dogs, has only rarely been known to infect humans. However, a recent case in the Yucatan Peninsula has brought about a very unique collaboration between medical practitioners and scientists.

Lagochilascaris minor has been reported in the Americas, commonly in South America where the eggs have been found in public parks1. However, identifying L. minor with conventional methods can be misleading as they resemble other ascaridoid eggs.

When a 23-year old man from a village in the forests of southern Quintana Roo state (Yucatan Peninsula) came into the local hospital in July 2016, physicians were surprised to find that a parasite had destroyed the mastoid apophysis, the lateral sinus, and part of the cerebellum. After a radical mastoidectomy and medical treatment for 63 days, the patient made a full recovery. After removal, the parasite was identified as L. minor using DNA barcodes and morphology. While the method of infection is uncertain, it is thought to be through direct exposure to the eggs or through the consumption of uncooked meat from wild animals.

Coronal computerized tomography scan of the human patient. Arrow indicates destruction of the left mastoid bone.
PHOTO CREDIT: Hospital General de Chetumal, Mexico
While it has been a challenge to successful identify Nematoda using genetic markers in the past, high-quality DNA barcode sequences were obtained using semi-degenerate primers designed for micro-crustaceans2. A comparison with 81 ascaridoids obtained from the Barcode of Life Data System (BOLD) revealed its position in a unique clade, most closely related to Baylisascaris procyonis.

This is the first multidisciplinary study involving DNA barcodes as a diagnostic medical tool in a human patient. This field of research can be promising because we can get a precise identification of the parasites in any stage of their life cycle. Diagnosis using DNA barcoding will allow the recognition of the infection parameters, transmission, and more precise epidemiology of parasites. With this information, we can not only diagnose the disease but also prevent it by finding the infectious stages, the intermediate hosts, or the vectors in the environment.

All sequences of Lagochilascaris are in the public project ‘NECHE Lagochilascaris from Yucatan’ in BOLD. This study is published in the Journal of Parasitology.

References:

  1. de Moura MQ, Jeske S, Gallina T, Borsuk S, Berne MEA, Villela MM (2012) First report of Lagochilascaris (Nematoda: Ascarididae) eggs in a public park in Southern Brazil. Veterinary Parasitology 184(2-4): 359-361. https://doi.org/10.1016/j.vetpar.2011.09.019
  2. Prosser SW, Velarde-Aguilar MG, Leon-Regagnon V, Hebert PD (2013) Advancing nematode barcoding: A primer cocktail for the cytochrome c oxidase subunit I gene from vertebrate parasitic nematodes. Molecular Ecology Resources 13(6): 1108-1115. https://doi.org/10.1111/1755-0998.12082

Written by

David González-Solís

David González-Solís

El Colegio de la Frontera Sur, Chetumal, México

Manuel Elías-Gutiérrez

Manuel Elías-Gutiérrez

El Colegio de la Frontera Sur, Chetumal, México

Jenny Alejandra Prado-Bernal

Clínica Carranza, Chetumal, México

Miguel Alfredo García-de la Cruz

Hospital General Dr. Manuel Gea González, Ciudad de México, México

April 30, 2019
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A DNA Barcoding Review of the Entomofauna of Egypt

A DNA Barcoding Review of the Entomofauna of Egypt

A DNA Barcoding Review of the Entomofauna of Egypt

From insect diversity to pests to forensics, DNA barcoding plays a vital role in Egyptian biodiversity conservation and legislative protection efforts.
Egyptian hornet wasp (Vespa orientalis) predating on Dermaptera (Labidura sp.).
PHOTO CREDIT: Mohamed Gamal

Egypt has more than 23,587 identified plant and animal species in addition to thousands of algae, bacteria, and viruses1, and this unique biodiversity contributes to Egypt’s economy and supports the welfare of its citizens. Agricultural production accounts for more than 10 per cent of Egypt’s GDP while tourism revenues from marine activities on the Red Sea represent more than 30 billion LE annually. Protecting threatened species such as dolphins, sharks, and dugong contribute by more than 61 million LE per year and the marine fish production is estimated to be worth 5 billion LE2. Therefore, Egypt has paid particular attention to the conservation and legislative protection of its natural heritage.

Joining its International Barcode of Life (iBOL) partners, Egypt has been using DNA barcoding to better understand and plan for protection of biodiversity. So far, Egypt has published 20,980 DNA barcode sequence records, 25 per cent (5,368) of which have species names that represent 695 species.

In this review, we present an overview of the DNA barcoding carried out on the Egyptian entomofauna and introduce current advances of this promising technique. This review focuses on three main areas that highlight studies investigating insect diversity and distribution, insects in forensic applications as well as pest and parasite dynamics.

Insect diversity and distribution: DNA barcoding has been used to investigate the genetic diversity of Egyptian wasp populations with a wide geographical range3. Three species, Vespa orientalis, Polistes bucharensis, and Polistes mongolicus were accurately identified by their DNA barcodes with the COI phylogenetic signal revealing interesting insights across Jordan, Giza, Cyprus, and Greece. Despite the wide geographical range, only minor genetic diversity was observed among populations of the three wasp species, indicating unrestricted gene flow. 

DNA barcoding has also been used in a larger-scale insect diversity investigation in the understudied Saharo-Arabian zoogeographic region, revealing significant heterogeneity between Egypt, Pakistan, and Saudi Arabia4. The year-long deployment of Malaise traps in these countries collected 53,092 specimens, including 18,391 from Egypt. The DNA barcode sequences revealed the occurrence of 3,682 BINs belonging to 254 families. These results reflect the high species richness of the area, encouraging further research into biodiversity monitoring for the region.

Insects in forensic applications: The Egyptian Forensic Medicine Authority, the leading authority on forensic medicine in Egypt, handles a relatively large number of cases annually and relies on laboratories for assistance with molecular techniques to ensure fast and reliable identification of species of forensic interest (e.g. necrophagous insects). To date, few studies in Egypt have evaluated the use of DNA barcoding in the identification and establishment of reference libraries for insect species of important post-mortem interval indication.

PHOTO CREDIT: Samy Zalat

Egyptian records of blow flies (Calliphoridae). Maggots (larva) are scavengers and adults are plant visitors.

PHOTO CREDIT: Ramadan Mounir

Aly & Wen5 studied the applicability of a 296-bp cytochrome c oxidase I (COI) sequence as a reliable mitochondrial genetic marker for the identification of forensically important flies following previous research showing the efficacy of a short COI marker in this group6. The study analyzed 16 species of blowflies (Calliphoridae), flesh flies (Sarcophagidae), and house flies (Muscidae) originating from Egypt and China and concluded that a shorter COI fragment is simple, cheap, and reproducible but lacks agreement with traditional morphological classification. In a follow-up investigation, Aly7 examined the reliability of long (1173-bp) vs. short (272-bp) COI markers for 18 species of the same 3 dipteran families from Egypt and China. The results indicated that the longer COI marker performed better than the shorter marker for dipterous identification due to better monophyletic separation and concordance with taxonomic classifications.

A more in-depth survey of the genetic diversity of forensically important blowflies (Calliphoridae) revealed numerous haplotypes among 158 specimens collected from four locations in Egypt (Giza, Dayrout, Minya, and North Sinai)8. Three particularly important species (Chrysomya albiceps, Chrysomya , Chrysomya marginalis) were well-differentiated using COI supporting its use for subfamily-, genera-, and species-level identification of blowflies.

Most importantly for forensics use, COI is highly effective at identifying different developmental stages of forensically important flies, including larvae, pupae, and even empty, otherwise difficult to identify morphologically. Five different species of Diptera and their immature stages from Alexandria, Egypt including Chrysomya albiceps, Chrysomya megacephala, Calliphora vicina, Lucilia sericata, and Ophyra capensis, were correctly identified using mitochondrial DNA markers9.

Pest and parasite dynamics: DNA barcoding has also played an important role in the identification of pests and parasites. Seventeen species of mealybug pests (Hemiptera: Pseudococcidae) have been identified by DNA barcoding specimens collected from populations infesting various crops and ornamental plants in Egypt and France10. The genetic variation found between populations of the same species using a combination of three markers (28S-D2, COI, and ITS2) and morphological examination indicated cryptic taxa that might respond differently to management strategies.

High diversity and rapid diversification were found in the head louse, Pediculus humanus (Pediculidae: Phthiraptera)11. P. humanus includes two morphologically indistinguishable subspecies: the head louse, P. humanus and the body louse, P. humanus. By analyzing sequence diversity of two mitochondrial genes (COI, cytb) in 837 specimens of Pediculus humanus from Egypt, Pakistan, and South Africa, high diversity and the occurrence of five mitochondrial lineages was revealed with implications for the spread of disease.

Conclusion: DNA barcoding of crop pests and pollinators, in addition to disease-carrying insect-vectors, will continue to be the top priority for the Egyptian government. Egypt actively enacts laws, carries out research, increases public awareness, engages local communities in the management of protected areas, and implements projects funded by Egypt and other international donors to protect biodiversity. These motivations place Egypt in a valuable position among other countries joining iBOL in support of BIOSCAN, a project that will build a global monitoring system for the planet.

References:

1. Egypt’s Fifth Biodiversity National Report (2014). Ministry of Environmental Affairs, Cairo, Egypt.

2. Coastal and marine biodiversity in Egypt (2018). United Nations Convention on Biological Diversity Conference (CBD COP14), Sharm El Sheikh. Ministry of Environment.

3. Abdel-Samie E, ElKafrawy I, Osama M, Ageez A (2018) Molecular phylogeny and identification of the Egyptian wasps (Hymenoptera: Vespidae) based on COI mitochondrial gene sequences. Egyptian Journal of Biological Pest Control. 28: 36. https://doi.org/10.1186/s41938-018-0038-z

4. Ashfaq M, Sabir JSM, El-Ansary HO, Perez K, Levesque-Beaudin V, Khan AM, Rasool A, Gallant C, Addesi Jo, Hebert PDN (2018) Insect diversity in the Saharo-Arabian region: revealing a little-studied fauna by DNA barcoding. PLoS ONE 13(7). https://doi.org/10.1371/journal.pone.0199965

5. Aly SM, Wen J (2013) Molecular identification of forensically relevant Diptera inferred from short mitochondrial genetic marker. Libyan Journal of Medicine 8:10. https://doi.org/10.3402/ljm.v8i0.20954

6. Zehner R, Amendt J, Schutt S, Sauer J, Krettek R, Povolny D. (2004) Genetic identification of forensically important flesh flies (Diptera: Sarcophagidae). International Journal of Legal Medicine 118(4): 245–247. https://doi.org/10.1007/s00414-004-0445-4

7. Aly SM (2014) Reliability of long vs short COI markers in identification of forensically important flies. Croatian Medical Journal. 55(1): 19–26. https://doi.org/10.3325/cmj.2014.55.19

8. Salem A, Adham F, Picard C (2015) Survey of the genetic diversity of forensically important Chrysomya (Diptera: Calliphoridae). Journal of Medical Entomology 52(3):320–328. https://doi.org/10.1093/jme/tjv013

9. Abdel Ghaffar HA, Moftah MZ, Favereaux A, Swidan M, Shalaby O, El Ramah S, Gamal R (2018) Mitochondrial DNA-based identification of developmental stages and empty puparia of forensically important flies (Diptera) in Egypt. Journal of Forensic Science & Medicine 4(3): 129–134. http://www.jfsmonline.com/text.asp?2018/4/3/129/242508

10. Abd-Rabou S, Shalaby H, Germain J, Ris N (2012) Identification of mealybut pest species (Hemiptera: Pseudococcidae) in Egypt and France, using a DNA barcoding approach. Bulletin of Entomological Research 102(5):515–523. https://doi.org/10.1017/S0007485312000041

11. Ashfaq M, Prosser S, Nasir S, Masood M, Ratnasingham S, Hebert PDN (2015) High diversity and rapid diversification in the head louse, Pediculus humanus (Pediculidae: Phthiraptera). Scientific Reports, 14188. https://doi.org/10.1038/srep14188

 

 

 

 

 

 

 

 

 

 

 

Written by

Samy Zalat

Samy Zalat

Zoology Department, Faculty of Science, Suez Canal University, Ismailia, Egypt.

Mona Mahmoud

Mona Mahmoud

Nature & Science Foundation, Cairo, Egypt.

April 7, 2019
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https://doi.org/10.21083/ibol.v9i1.5515

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