Faculty of Allied Medical Sciences Parasitology (MLPR-201) fall 2013/2014

1. Faculty of Allied Medical SciencesParasitology(MLPR-201)fall 2013/2014

2. Arthropods as Vectors of the Etiologic Agent of Diseases Dr. HamdyBadie M. El-Wakil Prof. of Parasitology & Public Health . Faculty of Allied Medical Sciences. Pharos University In Alexandria,Egypt

3. Intended Learning outcomes • By the end of this lecture the student should understand Arthropods as Vectors of the Etiologic Agent of Diseases

4. C - General Characters of Arthropods: • All arthropods, while varying considerably in size and shape, have certain features in common. They are all bilaterally symmetrical and metamerically segmented. They have externally a hard chitinous exoskeleton, sometimes sclerotized or calcified, inside which a hollow blood cavity is containing a clear fluid haemolymph. Arthropods have an excretory system, but a few of them consist of the malpighian tubules (2 or more), which lie in the hemocele and open into the hindgut near its junction with the midgut. They discharge the liquid wastes into the hindgut.

5. Respiration may be achieved by a variety of methods e.g. via gills, lung books, gaseous exchange, through the cuticle or by means of spiracles. Circulatory system consisting of heart, aorta, and sometimes-paired blood vessels that opens into the hemocele, which extends into all parts of the body. The blood consists of plasma and amoeboid white cells; respiratory pigment is hemocyanin in the plasma rather than hemoglobin in the case of gill routing and book lung-breathing.

6. The forth system, called central nervous system which consists of a dorsally situated composed of dorsal and ventral fused cephalic ganglia "Brain" connected by circumesophageal commissures to the media ventral paired nerve trunk, and to twinned ganglia of each post-cephalic body system. Nerve fibers extend from the central nervous system to all important organs and tissues. Either in many groups, there are light-sensitive organs in the head individual eyespots (ocelli) or compound eyes composed of ommatidia. All arthropods have jointed appendages, which may take the form of legs, antennae, mouthparts or cerci. The sexes are always separates and morphologically distinguishable.

7. Two different types of development take place: • 1- Incomplete metamorphosis: Hatched larvae resemble the adults but are smaller and gradually increase in size by successive molting e.g. Ticks. • 2- Complete metamorphosis: Hatched larvae are completely different morphologically from the adults. They may be worm like, transform to the inactive pupal stage from which finally the adults emerge, e.g. House fly.

8. D-Arthropods of medical importance: • They are Included in the Following Classes: • i- Class Insecta or Hexapoda e.g. house fly, fleas, lice, bugs, mosquitoes and flies (venomous, biological and mechanical vectors, intermediate hosts, and parasitic. • ii- Class Archanida e.g. scorpion, spiders, ticks and mites. • iii- Class Crustacea e.g. crabs, prawns and copepods. • iv. Class Chilopoda e.g. censpodes (venomous). • v. Class Pentatomida e.g. tongue worms (Endoparasitic).

9. Relation of the Pathogen to its Host: • The broad sense of the word, in one way or another may be considered parasites. The arthropod itself as a parasitic or else it transmits a parasitic infection. • 1- Ectoparasites: parasites, which live either temporally or permanently on the outside of the body e.g. the lice. • 2- Endoparasites: which live within the body e.g. Tongue worms (Pentastomida). • 3- Obligatory parasites: This forced to remain during their entire life in or on the body of the host e.g. both biting and sucking lice.

10. 4- Facultative parasites: which are able to exist as free-living organisms and they can be live as parasites e.g. the larvae of blowflies and flesh flies. 5- Intermittent parasites: which prey upon the host only at time and are free-living during intervals between meals e.g. bed bugs. 6- Transitory parasites: which are refer to cases in which the organism is parasitic during only a part of its life history e.g. Bot flies. Parasites are adapted to their mode of life in two general respects; physiologically and morphologically

11. The Arthropod-Transmitted Pathogens: • The groups of parasites served by arthropods are as follows: • 1- Protozoa: e.g. Entamoeba, Plasmodium, Trypanosoma and Leishmania. Several different groups of insects are involved as vectors for these protozoans’ diseases. • 2- Helminthes: e.g. tape worms, flukes, round worms and spiny-headed worms. Arthropods may be involved either as vectors or as intermediate hosts. • 3- Bacteria: e.g. Pasterurella (plague and tularemia bacilli), Shigella (dysentery), Salmonella, and others. Several groups of arthropods are involved as vectors.

12. 4- Spirochaetes: e.g. Treponema pertenue, the causal agent of Yaws, transmitted sometimes by flies and Borrelia recurrentis, the causative agent of Relapsing fever, transmitted by lice (Pediculus humanus) or Ticks (Ornithodorus spp.) 5- Bastonella bacilliformis: the causal agent of Carrion's disease transmitted by Phlebotomus. 6- Richettsiae: the causal agent of Typhus, scrub typhus, spotted fever, Q. fever and related infections; louse, mite, or tick. 7- Viruses: The causal agents of yellow fever, dengue the encephalitade and related infection of Colorado tick fever, phlebotomus fever and others. Mostly mosquito-born, but ticks phlebotomine sand flies and perhaps other vectors are involved.

13. Vector Effectiveness: • The variability in vectors effectiveness is attributed to several factors that are: • 1- Longevity: as long as the life of vector has been extended, this helps it to transmit the pathogens. • 2- Pathogen receptivity: the availability of vector to transmit the pathogen and the pathogen found it suitable for development or suitable habitat. • 3- Host specify : host preference. • 4- Frequency of feeding. • 5- Mobility and rate of speed. • 6- Numbers. • 7- Physiological and behavioral plasticity. • 8- Absence or presence of natural enemies. • 9- Vertical transmission; Transovarian transmission. • 10- Vectorial capacity; means that all the previous factors are all together in the same place and the same time.

14. Assignments • Group of students are selected every week to prepare a short seminar about his/her point of interest in one of the lecture topics. That to be

15. Recommended text books: • World Health Organization, Geneva. Basic laboratory methods in medical parasitology. 1991. • Larry Roberts and Jr.,John Janovy. Foundations of Parasitology. 2009 • Burton J. Bogitsh and Clint E. Carter. Human Parasitology. 2010