The document discusses treatment and control methods for parasites. It covers the importance of understanding parasite life cycles for effective treatment and control. It describes properties of ideal antiparasitic drugs, including being able to kill 100% of parasites, having a broad spectrum of action, rapid action, providing long-lasting protection, being simple to administer, requiring few treatments, being safe with minimal side effects, being affordable, and not having contraindications. The document also discusses how a parasite's life cycle can influence its treatment and control.

1. TREATMENT AND CONTROL METHODS IN
PARASITOLOGY
1 Part 1: Antiparasitic

2. INTRODUCTION
 There is a wide variety of parasites and an equally wide
range of substances and practices used in their treatment
and control.
 Focus on general concepts and also introduce some of
the most recent advances in parasitology for treating and
preventing parasitic infections.
 Part 1: Treatment
 Part 2: Control
 Part 3: Recent advances
2

3. IMPORTANCE OF UNDERSTANDING PARASITE LIFE CYCLES
FOR EFFECTIVE TREATMENT AND CONTROL
 To understand parasite life cycles  it is complicated
 Without knowledge of a parasite’s life cycle, one cannot
begin to understand how it is transmitted and how it
cause disease.
3

4.  For example in UK, rainfall and temperature are the key factors
determining the transmission efficiency of Fasciola hepatica –
principally through their effect upon the snail intermediate host.
 This factor has enabled the development of a liver fluke
forecasting scheme.
 Which is operated by National Animal Disease Information
Service (NADIS).
 So farmers can use this to determine when their flock is most
at risk of infection and therefore should be treated with
anthelmintics or if possible moved to less risky pasture.
4

5. HOW A PARASITE’S LIFE CYCLE CAN INFLUENCE
ITS TREATMENT AND CONTROL?
 Direct life cycle
 Life cycle involves one or more species of vector
 Life cycle involves one or more intermediate hosts
 Parasite has a variety of definitive hosts
 Parasite has life cycle stages that are exposed to the
environment
 Sequence and timing of life cycle stages within a host
 Location within host
5

6. DIRECT LIFE CYCLE
 Importance in treatment/ control
- Provision of sanitation and basic hygiene practices can
prevent many gastrointestinal parasitic diseases
 Application of life cycle knowledge
- Washing fruit and vegetables in clean water can remove
protozoan cysts and helminth eggs
6

7. LIFE CYCLE INVOLVES ONE OR MORE SPECIES OF
VECTOR
 Importance in treatment/ control
- Disease transmission can be controlled by targeting the
vectors
 Application of life cycle knowledge
- Bed-nets can prevent mosquitoes transmitting malaria
7

8. LIFE CYCLE INVOLVES ONE OR MORE
INTERMEDIATE HOSTS
 Importance in treatment/ control
- Disease transmission can be controlled by targeting the
intermediate hosts
 Application of life cycle knowledge
- Drainage to remove the habitat of snail intermediate
hosts of Fasciola hepatica
8

9. PARASITE HAS A VARIETY OF DEFINITIVE HOSTS
 Importance in treatment/ control
- Reservoir hosts are a potential source of infection
 Application of life cycle knowledge
- Schistosoma japonicum has numerous reservoir hosts
which can contaminate paddy field etc with eggs
9

10. PARASITE HAS LIFE CYCLE STAGES THAT ARE
EXPOSED TO THE ENVIRONMENT
 Importance in treatment/ control
- Environmental conditions can promote or limit infection
 Application of life cycle knowledge
- Composting can kill the infective stages of many
gastrointestinal parasites
10

11. SEQUENCE AND TIMING OF LIFE CYCLE STAGES
WITHIN A HOST
 Importance in treatment/ control
- Optimal time for diagnosis
 Application of life cycle knowledge
- Mf of Wuchereria bancrofti exhibits periodicity
11

12. LOCATION WITHIN HOST
 Importance in treatment/ control
- Optimal time for diagnosis
 Application of life cycle knowledge
- Cattle should be treated for warble fly infections before
the larvae reach their resting site
12

13. PART 1: TREATMENT
 Antiparasitic
- Chemical/ Pharmaceutical drugs
13

14. PROPERTIES OF AN IDEAL ANTIPARASITIC
DRUG OR TREATMENT REGIME
 Kills 100% of the parasites
 Broad spectrum
 Rapid action
 Provides long-lasting protection
 Simple to administer
 Requires only one or two treatments to achieve a cure
 Safe (does not cause harmful side-effects)
 Does not have contra-indications
 Affordable to the individual/population
 Chemically stable with a long shelf life
 Does not cause harm to the environment 14

15. KILLS 100% OF THE PARASITES
 Obviously drugs need to be effective
 Need to kill all the parasites found in (or on) the body of
the host
 Should be less harmful to the host cells than to the
parasites.
 This selective toxicity is hard to achieve for antiparasitic
drugs.
 For example praziquantel if only effective against adult
schistosomes but not good killing the developing
schistosomulae.
 If the drug is not effective killing 100% parasites, it will 15
increases the risk of resistance developing.

16. BROAD SPECTRUM
 Drugs that have a broad spectrum of action are beneficial
since they can be used to treat a variety of parasites.
 For example the avermectin drugs such as ivermectin
and doramectin  active against gastrointestinal
nematodes as well as ectoparasites such as lice, fleas
and ticks
16

17. RAPID ACTION
 Drugs that kill parasites rapidly reduce the chances of
resistance developing
 Since less time the parasite has to interact with the
drug, the less chance there is of it evolving a
physiological means of counteracting it.
17

18. PROVIDES LONG-LASTING PROTECTION
 Can reduce the cost of treatment
 Can protect the hosts from the same disease
infection.
18

19. SIMPLE TO ADMINISTER
 Drugs are seldom administered as compounds on their
own.
 Most of the drugs are ‘formulated’ with a cocktail of
chemicals
 The composition of which varies with the intended means
of delivery e.g liquid, tablet or injection
 Alters the effectiveness of the drug
 The formulation can influence drug’s stability, toxicity to
both host and target parasite, rate of absorption and
excretion, bioavailability and pharmacokinetics.
19

20.  Ease of administration is important in order to ensure
compliance and can be treated quickly with minimum of
fuss.
 Drugs can be taken without supervision tablets and
liquid
 Injection – intravenous or intra- peritoneal  supervised
by trained medical personnel
 For domestic animals  Dosing gun, ‘pour on/ spot on’
formulation on the body of animal, slow-release bolus 20
(placed the drugs into rumen using special device.

21. REQUIRES ONLY ONE OR TWO TREATMENTS TO ACHIEVE
A CURE
 The fewer the number of treatments required to remove the
parasite, the better the chance of patient compliance
 Especially if the treatment has to be delivered at a medical
centre or veterinary surgery
 If repetitive treatments are required, then there is a high
possibility that when the patient starts to feel better or animal
seems to be improving, the patient of owner will cease or
forget to complete the treatment regime.
 This will increase the possibility that the parasite will persist
and increases the chances of any resistance developing. 21

22. SAFE (DOES NOT CAUSE HARMFUL SIDE-EFFECTS)
 There is always a risk that the drugs will harm the hosts.
 The chance is reduced if the drug selectively acts upon a
physiological process that does not occur in the host.
 For example: Cryomazine and Diflubenzuron  targeting
the moulting process in arthropods
- Safe to use in mammal because no comparable
metabolic pathway.
- Cryomazine  interferes with the deposition of chitin in
the cuticle
- Diflubenzuron  inhibits chitin synthesis
22

23. DOES NOT HAVE CONTRA-INDICATIONS
 All chemicals are toxic if taken in sufficient concentration.
 It is very rare for the drug to be so specific that only
interacts with a single physiological process.
 Patients normally will cease treatment if the drug induces
unpleasant side effects such as nausea and vomiting.
 The host’s health and generic constitution can influence
the way it respond to drugs.
23

24.  For example: Ivermectin – is considered safe for use in
most mammals.
 In certain breeds of domestic dogs, very low
concentration induce neurological symptoms –e.g
hypersalivation, ataxia, blindness, respiratory distress,
which can be fatal.
24

25. AFFORDABLE TO THE INDIVIDUAL/POPULATION
 Cost, a major consideration for any treatment regime –
especially for poor people living in developing countries.
 Even if the drug is ideal in every way, if it is too expensive then
it becomes irrelevant to all but those who are rich.
 Drugs that are still in patent are usually expensive  the
manufacturer needs to make sufficient profit to recoup the
costs of development and fund the development of new drugs.
 Once drug is out of patent it can be manufactured by any
commercial concern and its cost usually declines.
25

26.  Example : albendazole and praziquantel
- In the early 2000s, tablets of albendazole  US$0.20
per tablet and praziquantel  US$3.00 per tablet.
- When out of patent, tablets of albendazole  US$0.02
per tablets and praziquantel  US$0.07 per tablets.
26

27. CHEMICALLY STABLE WITH A LONG SHELF LIFE
 The cost of drug is partly linked to its chemical stability.
 If the drug is stable and has a long shelf life, and does not
need to be stored in a fridge is usually going to be
cheaper.
 It can be bought in bulk and can be stored and
transported at low cost.
 It also will instantly available when needed.
27

28. DOES NOT CAUSE HARM TO THE ENVIRONMENT
 The environmental impact of the drug should be
considered.
 All the drugs that go into us and our animals are
ultimately passed out of us in one way or another and
they enter the environment.
 Sometimes drug are metabolized completely
 But very often breakdown products or unmetabolized
drug are passed in urine or faeces or in the milk or
present in the meat. 28

29.  Residues of drugs can persist in the environment under
suitable conditions.
 Therefore affect susceptible invertebrates both in soil and
in surrounding water systems.
29

30. Anticipated exposure routes of veterinary drugs in the environment 30

31. ANTIPARASITIC
 Antiparasitics are a class of medications which are indicated
for the treatment of parasitic diseases such
as nematodes, cestodes, trematodes, infectious protozoa
and amoebas.
 There are different medications suited to different types of
parasites.
- Antinematodes  are one group that can address infection
with nematodes
- Anticestodes  these target tapeworms
- Antiprotozoal  treat parasitic infections caused by protozoa
that enter the body
- Antitrematodes  treat parasitic infections caused by
trematodes 31

32. ANTIPROTOZOAL
 Kinetoplastid protozoa
 'Anaerobic' protozoa
 Sporozoan protozoa
32

33. KINETOPLASTID PROTOZOA
 Human sleeping sickness are usually treated with
suramin, though occasionally pentamidine is used.
 Where trypanosomes are present in the CNS, are treated
with melarsaprol or eflornithine (Trypanasoma brucei
gambiense infections only)
 Pentamidine  intramuscular injection
 Eflornithine is active by the oral route.
33

34.  Suramin is also used to treat trypanosome in infections in
equines and camels.
 Quinapyramine works well in camels, pigs and cattle, but
 Homidium bromide, isometamidium and diminazine aceturate
are the principal drugs used to control such diseases in sheep
and cattle
 Chagas disease  orally administered courses of nifurtimox or
benznidazole are effective.
 For leishmaniasis remains the antimonials  sodium
stibogluconate and meglumine antimonate  administered by
34
injection

35. 'ANAEROBIC' PROTOZOA
 Trichomoniasis, giardiasis and amoebiasis in both humans and
domestic animals can all be controlled by metronidazole.
 This drug is orally active, very efficacious and relatively free of side
effects.
 The alternative in giardiasis is mepacrine
 The alternatives in amoebiasis are diloxanide, which is only effective
in non-invasive cases, and tinidazole, which is another potentially
mutagenic 5-nitroimidazole.
 Subsequently, satranidazole, yet another 5-nitroimidazole, was
marketed in some territories for giardiasis and amoebiasis. 35

36. SPOROZOAN PROTOZOA
 Coccidiosis, especially in broiler chickens, is controlled by
the continuous administration of drugs in the diet.
 Currently, the ionophores such as lasalocid, salinomycin
and especially monensin are the coccidiostats of choice.
 Others, such as amprolium, clopidol, decoquinate and
robenidine, are however still used.
36

37.  Malaria, which is the most common of the parasitic diseases of
humans, can be treated by a wide range of drugs, all active by
the oral route.
 Until recently, the standard drugs were chloroquine for
treatment, ptimaquine to prevent relapse (Plasmodium vivax
malaria) and chloroquine or pyrimethamine + sulphadoxine
(Fansidar) or pyrimethamine + dapsone (Maloprim) for
prophylaxis.
 Babesiosis in cattle can be controlled by diminazine
aceturate, and theileriosis by parvaquone (East Coast Fever
only), buparvaquone and possibly halofuginone.
37
 Injectable formulations are available in all cases

38. ANTINEMATODES
 A large number of drugs are available to control the
gastrointestinal nematode infestations of domestic
animals.
 Piperazine (small animals), haloxon (horses), dichlorvos
(especially pigs), napbthalophos (sheep), the
benzimidazoles, the benzimidazole carbamates and their
prodrugs (e.g.
thiabendazole, albendazole, oxfendazole, fenbendazole),
morantel (cattle), pyrantel (horses and dogs), levamisole
and ivermectin.
38

39.  A large number of drugs are also available for the
treatment of human gastrointestinal infestations, including
piperizine, thiabendazole, albendazole, mebendazole, lev
amisole, pyrantel and bephenium.
 All are active via the oral route.
 The most commonly used is mebendazole, which
probably covers the broadest spectrum.
39

40.  Tissue-dwelling nematodes, the filariae
 diethylcarbamazine
 Adult worms can be eliminated with suramin
 Diethylcarhamazine was used also for onchocerciasis
 Ivermectin also might be macrofilaricidal.
40

41. ANTITREMATODES
 Sheep and cattle infected with liver fluke are
 likely to contain all three developmental stages:
1) early immature stages
2) immature stages
3) adults.
 Treatment of animals harbouring such mixed-stage
infections will be ineffective unless all three stages
are eliminated.
 Unfortunately most drug to treat trematodes
infection is a stage specific.
41

42.  Most drugs are active against the adults, including
rafoxanide, closantel, nitroxynil, nidoiolan, bromophos, bit
hinol sulphoxide, oxydozanide and albendazole.
 Diamphenethide is very effective against early immature
and immature stages, but is not against adults.
 Triclabendazole, however, works well against all stages.
 Fluke infections in humans are controlled by praziquantel
42

43.  The treatment of schistosomiasis in humans relies on three
drugs, oxamniquine, metrifonate and praziquantel.
 Oxamniquine works well against Schistosoma mansoni
 Metrifonate against S. haematobium
 Praziquantel against both species and also against S.
japonicum.
 All are active by the oral route and are generally well-
tolerated 43

44. ANTICESTODES
 A number of chemotherapies are available to control these
infections in both farm and companion animals, including
dichlorophen (mainly companion animals), niclosamide,
resorantel, bunamidine, mebendazole (sheep and cattle only),
nitroscanate (companion animals only), pyrantel (horses only,
at double dosage) and praziquantel (companion animals only).
 Key drugs for human use are niclosamide, albendazole and
praziquantel.
 All three drugs can be administered via the oral route, work
well against adult stages in the intestine and are generally well
tolerated.
44

45.  Niclosamide works only against adult worms in the gut;
 Albendazole and praziquantel can kill Taenia solium
cysticerci
 Mebendazole and especially albendazole are now being
used with some success in cases of hydatid disease due
to Echinococcus species
45

46. Antinematodes
Anticestodes Anthelmintics
Antitrematodes
46

47.  2 types
- Broad spectrum
- Narrow spectrum
47

48. BROAD SPECTRUM
Class Anthelmintic Mode of action
Benzimidazoles (BZs) Thiabendazole Bind to a specific
Fenbendazole building block called beta
Albendazole tubulin and prevent its
Oxfendazole incorporation into certain
cellular structures called
microbutbules, which are
essential for energy
metabolism
48

49. Class Anthelmintic Mode of action
Imidazothiaoles – Levamisole Mimic the activity of
tetrahydropyrimidines Morantel acetylcholine, a naturally
Pyrantel occuring
neurotransmitter that
initiates muscular
contraction
49

50. Class Anthelmintic Mode of action
Macrocyclic lactones (ML) Ivermectin Interfere with GABA-
Eprinomectin mediated
Doramectin neurotransmission,
causing paralysis and
death of the parasite.
50

51. Class Anthelmintic Mode of action
Amino-acetonitrile derivatives Monepantel It paralyzes worms by
(ADDs) attacking a previously
undiscovered receptor
HCO-MPTL-1, present
only in nematodes
51

52. Narrow spectrum anthelmintics
Anthelmintics Parasite covered
Triclabendazole Fluke (including immature fluke
from 2 days of age)
Closantel Fluke (including immature
fluke over 5 weeks of age),
Haemonchus contortus,
Nasal bots
Nitroxynil Fluke (including immature fluke),
Haemonchus contortus
Praziquantel Fluke and tapeworm
Diethylcarbamazine Filariasis worms
52