Economic Zoology
Economic Zoology is a sort of applied zoology , which involves the study of animals / living
organisms
that
are
of
benefit
or
those
that
cause
harm
to
humans
..
So , it is a specialized branch of zoology which deals with animal world that is associated
with the economy , health ,and welfare of humans . Actually , animal world is related to
economy by all means that we can count.
The economic value of an animal is generally accepted as the amount of money people are
willing to pay for it . In this modern world , perhaps it is the most popular way to assign value
to thing . But , certainly , each and every animal has righteous values and causes to live on
the Mother Earth with dignity .
The value of biodiversity can be separated into two categories i.e. Ethical value or intrinsic
value and Extrinsic value or anthropocentric value .
Ethical value or Intrinsic value is based on a respect for life, a reverence for the living world
and a sense of intrinsic value in nature and a concept of divine creation. It also defines the
existence value of an animal being .
Extrinsic value of an animal , which can be more clearly defined as Anthropocentric value ,
is comprised of direct and indirect economic benefit to humans .
Biodiversity provides a range of goods, from agricultural crops to medicines and fibers, to
which a direct value and cost can be assigned. This direct economic value of the natural
environment can be divided into those associated with consumption and production i.e.
Consumptive use and Productive use values.
Consumptive use value is usually assigned to goods consumed locally that are neither
sought nor sold and therefore do not contribute to the economy of a country. People living
off the land obtain the goods that they need for survival from the environment. Should the
environmental quality decline, for whatever reason, their standard of living would obviously
deteriorate.
Productive use values are assigned to those goods harvested from the environment, which
are bought and sold locally, nationally or internationally. Major products include construction
timber, fuel wood, fish and shellfish, fruits and vegetables and seaweed, to name a few. The
value of these products is determined not by the final retail cost of the product but by the
amount paid at the first point of sale less the expenses to that point.
Indirect
value
of
biodiversity
can
be
discussed
under
following
headings
Aesthetic value ( butterflies, nudibranches, ornamental fishes, birds, mammals , all lives in
the
wilderness
etc
Cultural value ( in various tribes , many animals are regarded as sacred creatures )
Ecological value ( many organisms are considered as bio-indicator, though each and every
animal has more or less impacts on environments.)
In a broad sense, according to economic importance, animals can be categorized under
following
i.
divisions:
Animals
ii.
iii.
for
food
Economically
and
harmful
Animals
of
products
animals
aesthetic
importance
iv. Animals in scientific research
Animals for food and products :
Many animals are useful to man because of their value as food . Almost every phylum or
animal group contains species that provide us with food or other important products . These
animal groups include shellfishes ( lobsters, shrimps, edible oysters ), fish, turtles, frogs,
birds and mammals . Of course , we largely depend upon fish and domesticated bird and
mammals
for
supply
of
meat
and
protein
food
However , there are many other animals that are associated with food chain of our food
supplying animals in the ecosystem. So, these animals indirectly help us in the production of
food .
Animal products that are more or less important , among these sponges, corals, shells of
mollusks, pearls, honey, wax, silk, shellac, feathers, wool, leather, bones etc are notable .
Economically harmful animals :
Numerous animals are directly or indirectly affect our health , community and other assets .
They
can
be
predators
parasites
or
pests
Many predators attack or kill wildlife or our domestic animals .
Many venomous animals can also be a threat to human . However, these predators and
venom bearers can be threat only when they are provoked .
The parasites not only attack our wild fauna and domesticated animals but also can infect
man . Concisely, we can tell that parasitic creatures largely belong to Protozoa,
Platyhelminthes, Nematoda and Arthropoda ( particularly the insects and the arachnids )
Animals of aesthetic importance :
Many animals and animal products are valuable to us in different ways . They are source of
our recreation, decoration and other forms of joy and pleasure. Ornamental fishes, birds,
reptiles, mammals are always in the centre of attraction to human.
Life in the wilderness always offer heavenly beauty . Tropical rain forests , swamp forests ,
tropical wetlands/Backswamps, forests of tundra biome , deserts , prairies , coral reefs ,
deep blue seas are the real heavens of Earth and they can hardly be described by words .
Besides , Communities of hobbyists are built up all over the world. Because of their
enthusiasm, through selective breeding, many color variants / morphs of organisms become
much popular in the hobby world .To describe a few , the astounding and jaw-dropping
beauty , striking coloration of several morphs of Dwarf python (Python regius), glowing
feathers (seems like they are painted by an artist) of tiny little budgies (Melopsittacus
undulatus) or aristocrat movement of male Siamese Fighter ( Betta splendens)
are
enough to make a person love and get tangled with this colorful world.
Public aquariums, Zoos, Safari parks are very much important now-a-days to make the
youth concern and feel about the wildlife that always remain entangled with mankind with
silence .
Animals in scientific researches :
Many animals have been used and still be used for scientific researches . our knowledge in
heredity and genetics are largely based on researches on Drosophila sp. or fruit fly.
Experiments in animals have always been helped in understanding , most of the most of the
physiological process. In medical science, surgery and drug effects are first observed on
several animals such as rats, monkeys etc . Generally , effectiveness of anti-venom serum
is examined on horse .
Besides , certain vaccines have been developed from animal serum . In present space
research monkeys, dog, toads, spiders etc have been used assess the effects of long space
journeys .
Glossary:
Economic (adj.) Of or relating to the production, development, and management of material
wealth, as of a country, household, or business enterprise.
Economical (adj.) Intended to save money, as by efficient operation or elimination of
unnecessary features
Economics i.e. the social science that analyzes the production, distribution, and
consumption of goods and services
Intrinsic value i.e. an ethical and philosophic property. It is the ethical or philosophic value
that an object has in itself or for its own sake, as an intrinsic property. An object with
intrinsic value may be regarded as an end or end-in-itself.
Extrinsic value i.e. the value of objects, both physical objects and abstract objects, not as
ends-in-themselves but a means of achieving something else. It is often contrasted with
items of intrinsic value.
PIROPLASMOSIS
Equine piroplasmosis is caused by the protozoan parasites Theileria
equi (formerlyBabesia equi) and Babesia caballi, which is approximately twice the size of T.
equi. EP affects horses, donkeys, mules, and zebras and sometimes dogs. The wild zebra
population is an important reservoir for the disease in Africa. Adult and nymphal ticks are
capable of transmitting the disease. While obtaining a blood meal from an infected horse, the
tick ingests infected equine red blood cells. As the erythrocytes are digested in the ticks
digestive tract, parasite trophozoites are released and undergo sexual reproduction, resulting
in the production of zygotes. Zygotes develop into sporozoites, which undergo division and
spread via the ticks haemolymph to its salivary glands. The causative agents are then
transmitted when the infected tick bites a susceptible horse.
Genera of ticks that transmit EP agents includeDermacentor, Hyalomma,
Rhipicephalus, and Boophilus. Approximately 15 species of ticks are capable of transmitting
EP agents.
Once infected, a horse can take 7 to 22 days to show signs of illness. Clinical signs of
acute EP arenonspecific, and mimic many other diseases and conditions. Signs observed are
the result of red blood cell destruction, complement activation, and release of inflammatory
mediators (including bradykinin, histamine, and 5-hydroxytryptamine). The severity of clinical
signs reflects the number of cells destroyed and the degree of activation of the complement
and inflammatory cascades.
Treatment via medication is instituted in affected horses. Diminazene diaceturate,
phenamidine isethionate, and amicarbalide diisethionate are effective in eliminating clinical
signs of B. caballi infection. Buparvaquone and other antitheilericidal drugs demonstrate
some efficacy against T. equi, and may eliminate the parasite when combined with
imidocarb. Theileria equi is more refractory to treatment than B. caballi, and higher dosages
of imidocarb are required.
Because EP agents are transmitted by ticks, tick control is a vital preventive
measure. Infected horses must be quarantined and isolated to reduce exposure to ticks. Pets
and wildlife, including rodents must be prevented from entering the isolation area, as they
may carry ticks capable of transmitting EP agents. No vaccine is available.
THEILERIASIS
Theileriasis, also called east coast fever, is a tick born disease of cattle, sheep and goats
caused by protozoan blood parasites, Theileria annulata, Theileria parva andTheileria ovis of
the Genus Theileria, Family Theileriidae and Order Piroplasmida.
Animals are infected through the bite of vector ticks.
Ticks possess large numbers of infective parasite Sporozoites, which develop in the
salivary glands during the first two to four days of engorgement of nymph or adult ticks. The
first visible stages are found in lymphocytes and the infected lymph nodes shows an increase
in mitotic figures. Within next several days parasites are increasingly apparent in the local
nodes and elsewhere in the lymphoid and reticulo-endothelial tissue.
Clinical signs include loss of appetite, dullness, depression, high temperature,
salivation, lacrimation, difficulties in breathing, anaemia, haemoglobinuria, jaundice,
convulsion and death. Other symptoms include, enlargement of lymph glands, pale mucous
membrane and nodules in the skin, enlargement of liver, spleen, kidney and gall bladder and
presence of necrotic ulcers in the abomasums of stomach.
Diagnosis involves microscopic examination of blood with Giemsas stain, presence
of punched necrotic ulcers in abomasum of dead animal and serological test
Treatment is done by administering Oxytetracycline, Berenil, Antihistamins and
Multivitamins.
TRYPANOSOMIASIS
Animal trypanosomiases include the following: Chagas; Nagana or Animal African
trypanosomiasis, also called Souma or Soumaya in Sudan; Surra; Mal de caderas of
central South America; Murrina de caderas of Panama; Dourine; Cachexial
fevers;Gambian horse sickness of central Africa; Baleri of Sudan;
Kaodzera or Rhodesian trypanosomiasis; Tahaga of camels in Algeria; Galziekte or bilious
fever of cattle or gall sickness of South Africa and Peste-boba of Venezuela.
African animal trypanosomiasis (AAT) is a disease complex caused by tsetse-flytransmitted Trypanosoma congolense, T. vivax, or T. brucei in cattle but can cause serious
losses in pigs, camels, goats, and sheep. Infection of cattle results in acute or chronic
disease characterized by intermittent fever, anemia, occasional diarrhea, and rapid loss of
condition and often terminates in death. In southern Africa the disease is widely known
as nagana, which is derived from a Zulu term meaning to be in low or depressed spirits a
very apt description of the disease.
Ruminants are widely known to be active reservoirs of the trypanosomes. Wild
Equidae, lions,
leopards, and wild pigs are all susceptible
and can also serve as carriers of trypanosomes. Of the three African animal trypanosomes,
only T. vivax occurs in the
western Hemisphere in at least 10 countries in the Caribbean and South and Central
America.
In Africa, the primary vector for T. congolense, T. vivax, and T. brucei is the tsetse fly. These
trypanosomes replicate in the tsetse fly and are transmitted through saliva when the fly feeds
on animals. The three main species of tsetse flies for transmission of trypanosomes
are Glossina morsitans, which favors the open woodland of the savanna; G. palpalis, which
prefers the shaded habitat immediately adjacent to rivers and lakes; and G. fusca, which
favors the high, dense forest areas. Trypanosomiasis is also mechanically transmitted by
other biting flies of the genera Tabanus, Haematopota, Liperosia,
Stomoxys and Chrysops flies.
Initial replication of trypanosomes is at the site of inoculation in the skin, where
swelling and a sore is caused. Trypanosomes then spread to the lymph nodes and blood and
continue to replicate. T. congolense localizes in the endothelial cells of small blood vessels
and capillaries. T. brucei and T. vivax localize in tissue. Antibody does not clear the infection,
for the trypanosome has genes that can code for many different surface-coat glycoproteins
and change its surface glycoprotein to evade the antibody.
The cardinal clinical sign observed in AAT is anemia. Within a week of infection,
there is usually a pronounced decrease in hemoglobin, red blood cell, and white blood cell
levels, and within 2 months these may drop to below 50 percent of their pre-infection values.
Also invariably present are intermittent fever, oedema and loss of condition.
In the early phases of infection, especially with T. vivax and T. congolense, the parasite can
readily be observed by microscopic examination of a wet-mount of blood slides. Thick blood
films and stained with Giemsa are also a good technique.
Fly eradication and drug prophylaxis are effective trypanosomiasis control methods. Some of
the older drugs such as the quinapyramine derivatives Antrycide andAntrycide Prosalt are
still used and give effective protection against T. brucei infection in horses, camels, and
cattle. The drug pyrithidium bromide is useful in the prophylaxis ofT. vivax and T.
congolense infections in cattle, sheep, and goats and can give protection for up to 6 months.
The most widely used of the newer drugs is isometamidium chloride.Homidium
bromide has also been found to be an effective drug in Kenya, and the newly introduced
arsenical Cymelarsan is effective in treatment of T. brucei infection. A very widely used drug
is diminazine aceturate, which is effective against all three African animal trypanosomes.
The isometamidium drugs are also excellent chemotherapeutic agents as are the
quaternary ammonium compounds Antrycide, Ethidium andProthidium.
No vaccine is currently available for African animal trypanosomiasis.
COCCIDIOSIS
Coccidiosis is the name given to a group of closely related diseases caused by a protozoan
parasite called Eimeria, which develops inside cells lining the intestine. As the parasites
reproduce they cause bleeding and massive swelling of the gut. This leads to a huge loss of
liquid and the bird is unable to absorb the nutrients from its food. Out of 11 species of
Coccidia, the most common species are Eimeria tenella, E. acervulina and E. maxima, which
cause chronic intestinal coccidiosis.
Eimeria tenella develops in the cells of the cecca which are the two blind sacs near the end
of the intestine. It is one of the most pathogenic coccidia to infect chickens.
E. necatrix develops in the small intestine and later in the caecum, within deeper tissues of
the small intestine and is a major pathogen of poultry.
E. accervulina and E. maxima develop in epithelial cells, primarily in the upper part of the
small intestine.
The Sporozoite stage is the infective stage that contains special proteins and
enzymes that allow it to penetrate the cell wall. Once inside the cell the sporozite begins its
development through various stages. More parasites are produced during these stages, they
in turn move on and in to healthy cells to begun the cycle again. The result is weakened cell
walls that allow moisture to leak and damaged blood vessels. This loss of blood and fluid is
often fatal to the bird. Coccidiosis is passed to another bird during the oocyst stage, which is
an egg-like structure that is excreted by the bird and can remain inactive for many weeks and
still infect another bird. The infection starts when an oocyst is ingested. Once ingested,
symptoms may appear as early as 4-6 days later.
Symptoms of the disease include listlessness, lethargy, weight loss and blood in the
droppings or elsewhere in the body, diarrhoea, and dehydration are all common signs of
Coccidiosis. The birds may also appear to have dirty or wet vents and may eventually die.
A controlled dose of coccidial vaccine is administered once to day-old chicks,
initiating the development of natural immunity against Eimeria. Vaccination eliminates the
need for withdrawal times, which are required when anticoccidials are used, as well as
concerns about possible drug residues in poultry meat. Vaccination is also used to restore
sensitivity to anticoccidials by replacing resistant, in-house strains of Eimeria with drugsensitive Eimeria strains.
LEISHMANIASIS
Leishmaniasis is primarily a zoonotic disease in which wild and domestic animals
such as the fox, jackal, rodents and wolves serve as reservoir hosts. Other animals in the
surrounding areas can become infected and these are referred to as secondary or incidental
hosts. The only proven vector of the Leishmania is the blood-sucking female sand fly of the
genus Phlebotomus in the old world and Lutzomyia in the new world.Visceral leishmaniasis is
caused by the parasites Leishmania donovani, Leishmania infantum and Leishmania
archibaldi in the old world and by Leishmania chagasi in the new world.
The sand fly vector becomes infected when feeding on the blood of an infected
individual or an animal reservoir host. The parasites live in the macrophages as round, nonmotile amastigote fiorm (3-7 micrometers). The macrophages are ingested by the fly during
the blood-meal and the amastigotes are released into the stomach of insect. Almost
immediately the amastigotes transform in to a motile, elongated (10-20 micrometers),
flagellate promastigote form. The promastigotes then migrate to the alimentary tract of the
fly, where they multiply by binary fission. Four to five days after feeding, the promastigotes
move forward to the proboscis of the insect. When the sand fly next feeds on a mammalian
host, its proboscis pierces the skin and saliva containing anti-coagulant is injected into the
wound to prevent the blood from clotting, the promastigotes are transferred to the host along
with the saliva. Once in the host the promastigotes are taken up by the macrophages where
they rapidly revert to the amastigote form. The leishmanias are able to resist the
microbiocidal action of the acid hydrolases released from the lysozymes and so survive and
multiply inside the macrophages, eventually leading to the death of the macrophages. The
released amastigotes are taken up by the additional macrophages and so the cycle
continues. Ultimately all the organs containing macrophages and phagocytes are infected,
especially the spleen, liver and bone marrow.
Common symptoms include high undulating fever often with 2-3 peaks in 24 hours
and drenching sweats which can easily be misdiagnosed as malaria; Chills, rigors, weight
loss, fatigue, poor appetite, cough, burning feet, insomnia, abdominal pain, joint pain,
anorexia, epistaxis and diarrhoea. Clinical sings include splenomegaly, hepatomegaly and
lymphadenopathy.
The two pentavalent antimonial compounds, sodium
stibogluconate andmeglumine antimoniate have been used as first-line chemotherapeutic
agents against all forms of leishmaniasis including visceral leishmaniasis. If treatment with
pentavalent antimonials is unsuccessful a preparation of an aromatic diamidine,
pentamidine isethionate (Pentamidine) or pentamidine dimethane sulphonate
(Lomidine) is used.Amphotericin B, which is a macrolide, is another drug of second choice
used in the treatment of leishmaniasis. There are three preparations of lipid associated
Amphotericin B currently under trial for treatment of leishmaniasis: AmBisome (Vestar,
USA), Amphocil(Liposome technology Inc, USA) and Amphotericin B lipid
complex (Bristol Meyers Squibb, USA).
Types of parasites
The major types of organisms that cause parasitic infections include species of protozoa,
helminths or worms, and arthropods.
Protozoa. Protozoa are single-celled organisms that carry out most of the same physiological
functions as more complex organisms. More than 45,000 species of protozoa are known,
many of which are parasitic. As parasites of humans, this group of organisms has historically
been the cause of more suffering and death than any other category of diseasecausing
organisms.
Intestinal protozoa occur throughout the world. They are especially common in areas where
food and water sources are subject to contamination from animal and human waste.
Typically, protozoa that infect their host through water or food do so while in an inactive
state, called a cyst. A cyst consists of a protozoan encased in a protective outer membrane.
The membrane protects the organism as it travels through the digestive tract of a previous
host. Once inside a new host, the parasite develops into a mature form that feeds and
reproduces.
Amebic dysentery is one of the most common parasitic diseases. It often afflicts travelers
who visit tropical and subtropical regions. The condition is characterized by diarrhea,
vomiting and weakness. It is caused by a protozoan known as Entamoeba histolytica.
Another protozoan that causes severe diarrhea is Giardia lamblia. This organism was
originally discovered by Leeuwenhoek and has been well-publicized as a parasite that can
infect hikers who drink untreated water.
Other types of parasitic protozoa infect the blood or tissues of their hosts.
These protozoa are typically transmitted through another organism, called
a vector. A vector is an organism that carries a parasite from one host to
another host. In many cases, the vector is an invertebrate, such as an
insect that itself feeds on a host and then passes the protozoan on
through the bite wound. Some of the most infamous of these protozoa are
the ones that cause malaria and African sleeping sickness.
Hosts
Giardia infects humans, but is also one of the most common parasites infecting cats, dogs and
birds. Mammalian hosts also include dozen of species,[5] including cattle, sheep,[6] andgoats.[6]
