Developement of Nematicide Resistance in Nematodes

1. Welcome…

2. Development of Nematicidal Resistance
in Nematodes
Manoranjan Dash
Roll No: 20577
Division of Nematology
Chair person: Dr. Uma Rao
Seminar leader : Dr. Harendra
Kumar

3. What is Resistance?
When a greater frequency of individuals in a
parasite population, usually affected by a dose or
concentration of compound, are no longer affected
(or a greater concentration of drug is required to
reach a certain level of efficacy)
Wolstenholme ,et al.2004

4.  Cross resistance
 Insects exhibiting resistance to one insecticide develop
resistance to other insecticides with the same modes of action
William et al.,1998
Types of resistance
Simple Resistance
 Multiple resistance
 Occurs in insect populations that resist two or more
insecticide classes with unlike modes of action
 Resistance limited to one insecticide and not related one’s
Monogenic Resistance
 Single gene involved in development of resistance
Polygenic Resistance
 Several genes involved in development of resistance

5. Two types-
1. Pre adaptive mechanism
2. Post adaptive mechanism
1.Pre adaptive mechanism:
 Also called as genetic mechanism – b/c resistant genes are already
present in the population and insecticides act only as selective agents
- kill the susceptible population
eg. Kdr genes confer resistance to DDT and Pyrethroids
Mechanism of Resistance

6. 2. Post adaptive mechanism
 Morphological resistance:
 Absorb toxin more slowly/less penetration
Behavioural resistance:
 Detect or recognize a danger and avoid the toxin
Metabolic resistance:
 Detoxify or destroy the toxin faster or quickly get rid of toxic
molecules of their bodies
 Target-site resistance:
 Prevent the insecticide binding or interacting at its site of action
Contd..

7. 1%
Hexapoda 85%
14%
OTHERS
INSECTA
ACARINA
Based on pesticide resistance data base Dec
2009
Pesticide Resistance in Arthropods

8. COLEOPTERA 15%
DIPTERA 39%
5%
Homoptera 12%
4%
LEPIDOPTERA 18%
PESTICIDE RESISTANCE IN HEXAPODA
COLEOPTERA DICTYOPTERA DIPTERA EPHEMEROPTERA
HEMIPTERA HOMOPTERA HYMENOPTERA LEPIDOPTERA
NEUROPTERA SIPHUNCULATA SIPHONAPTERA THYSANOPTERA
ORTHOPTERA
Based on pesticide resistance data base Dec
2009

9. Measures of resistance can be:
(i) Efficacy at a certain dose rate
(ii) Concentration required to kill 50% of worms in vitro
(iii) Proportion of farms with clinical resistance
Reduction in response can manifest in different
ways :
- Heritable decline in the efficacy of an anthelmintic against a
population of parasites generally susceptible to that drug
- Resistant populations requiring more frequent treatments
than previously administered.
(Silvestre &Cabaret. 2000)

10. Factors Affecting Rate of Spread Of
Resistance and its Effect
 Genetic factors
 Proportion of the population submitted to selection
pressure
 Persistence of the drug
 Mutation rate
 Dominance of the trait
 Reproductive factors
 Ecological factors
 Migration of parasite
 Ability to avoid the drug
 Number of generations per year
 Fluctuations in population size
 Operational factors
(Silvestre &Cabaret. 2000)

11. Three phases linked to the accumulation of
resistance alleles:
Phase 1
 Establishment of resistance is largely a random event
 Influenced by population size and diversity
 Mutation rate for the gene(s) in question
 Relative fitness of individuals with the mutation compared
with the wild-type gene
 Resistance allele frequency is usually low

12. Phase 2
 Development occurs in response to a selective agent
that kills susceptible worms, but allows resistant ones to
survive and reproduce
 Drug treatment a powerful selector of resistance alleles
 With continued selection, frequency of resistance alleles
increases and disperses through population
 Emergence occurs as selection continues and
resistance becomes noticed
 R alleles are at high frequency
Phase 3
Contd..

13. ANTHELMINTIC RESISTANCE IN
NEMATODE PARASITES OF
ANIMALS AND HUMANS(APNs)

14.  Anthelmintic resistance
 Most frequent in goats
 Less frequent in sheep and horses
 Least common in cattle
 Available anthelmintics are discriminated on the basis of
their mode of action
 BZ (Benzimidazole) bind selectively to beta-tubulin
 LEV (Imidazothiazole) is agonist at nicotinic
acetylcholine receptors
 AVM (Macrocyclic lactones) bind to receptors directing
chloride channels
 Nematode parasites infections affect all grazing
ruminants world-wide
Anthelmintic Resistance
(Silvestre &Cabaret. 2000)

15. Host s p e c i e s P a r a s i t e
genus
Benzimidazoles
(bz)
Imidazothiazole
s (lev)
Macrocyclic
lactones (avm)
Goat
Haemonchus R S R
Teladorsagia R R R
Trichostrongylus R R R
Sheep
Haemonchus R S R
Teladorsagia R R R
Trichostrongylus R R R
Horse Cyathostoma R R S
Cattle Cooperia R R S
Ostertagia R S R
Haemonchus S R S
Human Necator R S S
Ancyclostoma S R S

16. Cellular Reactions Leading to Drug Resistance in Eukaryotic Cells
Catherine,et al.,2007

17. Factors for Selection of Anthelmintic
Resistance in APNs
 Continuous use of a single drug family
 Treatment of the whole parasite population with no
refugia to escape selection pressure
 Under-dosing of drugs
 Migration of infected hosts introduces an important flow of
anthelmintic resistant gene in populations that are not
submitted to selection pressure by treatments
(Albonico et al., 1999; berrag et al., 2002)
(wyk, 2001)
(Barnes et al., 1995; silvestre et al. 2001)
(Varady el al, 1993)

18. NEMATICIDE RESISTANCE IN
FIELD CONDITIONS

19.  Resistance is more prone to be selected with persistent
compounds than with short-lived molecules
 On the basis of their mode of action, organophosphates and
carbamates are likely to induce nematicide resistance as these
compounds are highly persistent in comparison with
anthelmintics
 Nematodes that survive treatment have an enormous
reproductive advantage during persistency period and these
treatments should logically generate a highly efficient selection
pressure on nematode populations
NEMATICIDE RESISTANCE
Dobson et al., 1996

21. Case Study on Field
Resistance Development
in Nematodes

23. Materials and Methods
 3 plots (400 vines in each plot) ; 3 treatment
1st- Carbofuran
2nd-Phenamiphos
3rd-Untreated control
 Treated plots received Non Fumigant Nematicides
treatments annually
 8 vines randomly selected from 400 vines from each
plot and nematodes collected were counted
For Population studies

24.  200 vines sampled per plot
 Soil and root cores from ten vines were combined to
make one sample (20 samples per plot)
 Collected nematodes were evaluated for Meloidogyne,
Pratylenchus, Criconemella, Paratylenchus, free-living
dorylaims and free-living nondorylaim species
 All population levels were expressed as the number of
nematodes per 200 cm3 soil
Contd..

25. Result
 Population Levels
 In 1982 and 1984 population data was collected two months following
chemical treatment and carbofuran application appeared to have
reduced nematode levels in 1982 and 1984
 Sudden development of increased population levels in the carbofuran
plot in 1985 was noted
 Significantly higher numbers of free-living nondorylaims and free-living
dorylaims found in the carbofuran treated rows were found
 Low levels of Meloidogyne Pratylenchus and Criconemella species
were observed in samples taken from vines treated with carbofuran
(1985)

26. 102
75
29
56
50
91
0 0
43
1982 1984 1985
Field population Ievels of Xiphinema index
from a Zinfandel vineyard in Lodi, California
Wild Carbofuran-treated Phenamiphos treated

27. 33
76
2
6
2
18
33
free living
dorylaims
non dorylaims pratylenchus criconemella Meloidogyne
Field population Ievels of Xiphinema index
from a Zinfandel vineyard in Lodi, California
Carbofuran treated control

28. In vitro Tests for Resistance
Xiphinema index
 Nematodes from carbofuran treated plot
demonstrated greater tolerance to
carbofuran
 Response to oxamyl was not as well
defined
Meloidogyne incognita
 Nematodes from the carbofuran lot
demonstrated a higher tolerance to all three
nematicides
 Best expressed at the highest concentrations

29. 92 95
79
41
85 88
83 85
95 96 98
87
control 0.02mM 0.2mM 0.6mM
Carbofuran treatments
Xiphinema index
Wild Carbofuran Phenamiphos

30. 92 89
67
63
85 88
78
71
95 92
78
44
control 0.06mM 0.3mM 0.6mM
Xiphinema index
Wild Carbofuran Phenamiphos
Oxamyl Treatments

31. 92 89
67
63
85
89
56
14
95
87
10
1
control 0.032mM 0.96mM 0.16mM
Phenamiphos treatments
Xiphinema index
Wild Carbofuran Phenamiphos

32. 100 97
75
22
100 100 99
72
control 0.2mM 0.4mM 0.6mM
Carbofuran treatments
Meloidogyne incognita
Wild Carbofuran

33. 100
90
62
5
100 98
53
32
control 0.04mM 0.2mM 0.4mM
Oxamyl treatments
Meloidogyne incognita
Wild Carbofuran

34. 100
85
63
23
100 100
90
79
control 0.08mM 0.2mM 0.4mM
Phenamiphos treatments
Meloidogyne incognita
Wild Carbofuran

35.  Results from the current tests suggested development of
NFN resistance under field conditions does not require a
continuous monthly stressing regime
 Sufficient selective pressures were created in the vineyard
to favor resistance
 These developments may vary with the specific host,
nematode species and strain, nematicide, soil types and
related factors
 Concept of resistance should be considered in designing
future nematode control programs
Conclusion of the Study

36. Probable Reasons for Paucity of Nematicide
Resistance Developement
 Major reason for nematicide resistance being so rare has to do with the
reduced selection pressure by nematicides
 Due to parthenogenetic reproduction in many plant parasitic
nematodes, susceptible population towards nematicide will always
remain present in the field
 Fertility of PPN’s is less compared to APN’s which slows down
appearance of drug resistance genes
 Regulations are becoming more and more restrictive regarding usage
of nematicide in agriculture leading to alternatives to chemical control
being largely used in integrated control schemes
 Genetic Diversity of plant parasitic nematodes

37. The Way Out?
Less dependency on Chemical control of nematodes
Whenever chemical control is used:
 Use recommended dose
 Alternatively use chemicals with different Mode
of Action
 Use of new nematicidal Molecules
 Use of holistic approaches like Integrated Nematode
Management

38.  It seems then that even if nematodes populations do
acquire nematicide resistance in field conditions, it does
not threaten production thanks to alternative methods of
agricultural control for PPN’s
 Only one field nematicide resistance report can be
confirmed for PPN (Pratylenchus scribneri in Maize)
compared to 1,330 reports on anthelmintic resistance of
APN’s recorded from 1973 to 2002
Conclusion
(Smolik, 1978)