Your search found 13 records
1 Schousboe, M. L.; Rajakaruna, R. S.; Salanti, A.; Hapuarachchi, H. C.; Galappaththy, G. N. L.; Bygbjerg, I. C.; Amerasinghe, Priyanie; Konradsen, F.; Alifrangis, M. 2007. Island-wide diversity in single nucleotide polymorphisms of the Plasmodium vivax dihydrofolate reductase and dihydropteroate synthetase genes in Sri Lanka. Malaria Journal, 6(28). 6p.
(Location: IWMI HQ Call no: IWMI 614.532 G744 SCH Record No: H039911)
2 Rajakaruna, R. S.; Weerasinghe, M.; Alifrangis, M.; Amerasinghe, Priyanie; Konradsen, F. 2006. The role of private drug vendors as malaria treatment providers in selected malaria endemic areas of Sri Lanka. Journal of Vector Borne Diseases, 43:58-65.
Malaria ; Waterborne diseases ; Medicines ; Drugs / Sri Lanka / Anuradhapura / Ampara / Vavuniya / Mannar / Moneragala / Hambantota / Badulla
(Location: IWMI-HQ Call no: IWMI 616.9362 G744 RAJ Record No: H039914)
3 Rajakaruna, R. S.; Jayawardena, U. A.; Piyatissa, P. M. J. R.; Navaratne, A.; Amerasinghe, Priyanie. 2007. Trematode infections, biocides and amphibian deformities: evidence from an amphibian hotspot. [Abstract only]. Abstract of a paper presented at a Joint Meeting of Ichthiologists and Herpetologists, St. Louis MO, USA, 2007. 1p.
(Location: IWMI HQ Call no: IWMI 597.8 G000 RAJ Record No: H040820)
4 Rajakaruna, R. S.; Amerasinghe, Priyanie H.; Galappaththy, G. N. L.; Konradsen, F.; Briet, Olivier J. T.; Alifrangis, M. 2008. Current status of malaria and anti-malarial drug resistance in Sri Lanka. Ceylon Journal of Science (Biological Sciences), 37(1):15-22.
(Location: IWMI HQ Call no: IWMI 614.532 G744 RAJ, PER Record No: H041484)
http://www.sljol.info/index.php/CJSBS/article/viewPDFInterstitial/493/531
https://vlibrary.iwmi.org/pdf/H041484.pdf
https://vlibrary.iwmi.org/pdf/H041484.pdf
Even though malaria continues to cause high morbidity and mortality in most of the malaria endemic countries in the world, it is currently not a major health problem in Sri Lanka. Despite the low malaria incidence, the development and spread of anti-malarial drug resistance, combined with a recent increase in the armed conflict hindering provision of effective health services will make it difficult to control malaria in Sri Lanka. Since chloroquine (CQ) resistant Plasmodium falciparum was first reported from Dambulla area in 1984, the number has increased to more than 50% observed in vivo from various endemic areas. In concordance with this, single nucleotide polymorphisms (SNPs) in genes of P. falciparum responsible for CQ resistance are present. A limited number of trials have investigated the efficacy of the second line drug, sulfadoxine/ pyrimethamine (SP) against P. falciparum and a few cases of resistance have been reported. Moreover, SNPs in P. falciparum genes responsible for SP resistance are present and may constitute a sign of evolving SP resistance development. For P. vivax, drug resistance is not yet recorded as a problem in Sri Lanka, however the prevalence of SP resistant SNPs in P. vivax populations seems high and may pose a risk despite that SP is not used directly against P. vivax infections. Continuous monitoring of drug efficacy in vivo, as well by measuring the prevalence of SNPs related to drug resistance are major issues to be addressed.
5 Rajakaruna, R. S.; Piyatissa, P. M. J. R.; Jayawardena, U. A.; Navaratne, A. N.; Amerasinghe, Priyanie H. 2008. Trematode infection induced malformations in the common hourglass treefrogs. Journal of Zoology, 275:89-95.
(Location: IWMI HQ Call no: e-copy only Record No: H042478)
(0.57 MB)
Reports on malformations in amphibians due to trematode infections prompted this study on an endemic frog species in Sri Lanka. The effect of an infection with a monostome-type cercaria is reported here. Ten days post-hatch, tadpoles (Gosner stage 27) of the common hourglass treefrog Polypedates cruciger (Anura: Ranidae), were exposed to a monostome-type cercaria, in a dose-dependent manner, under laboratory conditions. Malformations, survival and growth of the tadpoles were monitored for four treatments having different doses of cercariae (control=0, low=16, intermediate=32 and high=48). The severity and the number of malformations varied depending on the dose of the infection. A higher percentage (90%) of malformations was observed at higher doses of cercariae. Overall, malformations in the limbs, spine and skin pigmentation were common after parasite exposure. Survival declined with increasing doses of parasite infections, declining to 88% in the high treatment group, although not statistically significant. The growth rates of tadpoles as measured by weight and snout to vent length showed that exposed individuals were significantly smaller and had higher variance in growth compared with that of the controls. Thus, this trematode infection significantly affected the growth and induced severe malformations in P. cruciger, under laboratory conditions. Such malformed tadpoles and adults may face high predation under natural conditions. Here, we present the first empirical evidence of the effect of a trematode infection on the development of malformations, growth and survivorship in an endemic amphibian species in Sri Lanka.
6 Jayawardena, U. A.; Rajakaruna, R. S.; Navaratne, A. N.; Amerasinghe, Priyanie H. 2010. Toxicity of agrochemicals to common hourglass tree frog (Polypedates cruciger) in acute and chronic exposure. International Journal of Agriculture and Biology, 12(5): 641-648.
(Location: IWMI HQ Call no: e-copy only Record No: H043540)
http://www.fspublishers.org/ijab/past-issues/IJABVOL_12_NO_5/1.pdf
https://vlibrary.iwmi.org/pdf/H043540.pdf
https://vlibrary.iwmi.org/pdf/H043540.pdf
(0.15 MB)
Direct effect of four common agricultural pesticides viz., chlorpyrifos, dimethoate, glyphosate and propanil, on the survival, growth and development of malformations in common hourglass tree frog, Polypedates cruciger (Anura: Ranidae) was studied under laboratory conditions in acute and chronic exposure. Acute exposure to high concentrations was carried out to determine the LC50. The 48 h LC50 of the pesticides were within the Pesticide Area Network specified limits, except for propanil. The percentage survival of the tadpoles under chronic exposure to ecologically relevant doses was lower (glyphosate 75%, dimethoate 77.5%, chlorpyrifos 80% & propanil 85%) than the control group (95.5%) and was significantly affected by the concentrations. Exposed tadpoles took more time to metamorphose and were significantly smaller in size than the control tadpoles. They also developed malformations at high frequencies (glyphosate = 69%, dimethoate = 64%, chlorpyrifos = 60%, propanil = 45%). Malformations were mainly kyphosis (hunched back), scoliosis (curvature), skin ulcers and edema. However, severe limb malformations were not observed in the study. Chlorpyrifos had a profound effect even at very low concentrations (0.05 ppm). This study provides the first empirical evidence of a comparative study on the effect of pesticides on an endemic amphibian species in Sri Lanka and underscores the importance of investigation the level of agricultural pesticides in freshwater ecosystems and their effect on non-target organisms.
7 Gunawardena, S.; Karunaweera, N. D.; Ferreira, M. U.; Phone-Kyaw, M.; Pollack, R. J.; Alifrangis, M.; Rajakaruna, R. S.; Konradsen, F.; Amerasinghe, Priyanie H.; Schousboe, M. L.; Galappaththy, G. N. L.; Abeyasinghe, R. R.; Hartl, D. L.; Wirth, D. F. 2010. Geographic structure of Plasmodium vivax: microsatellite analysis of parasite populations from Sri Lanka, Myanmar, and Ethiopia. American Journal of Tropical Medicine and Hygiene, 82(2):235-242. [doi: https://doi.org/10.4269/ajtmh.2010.09-0588]
Genetic variation ; Plasmodium vivax ; Parasites ; Public health ; Waterborne diseases ; Malaria ; Satellite observation ; Analysis / Sri Lanka / Myanmar / Ethiopia
(Location: IWMI HQ Call no: e-copy only Record No: H044535)
(1.07 MB) (1.07MB)
Genetic diversity and population structure of Plasmodium vivax parasites can predict the origin and spread of novel variants within a population enabling population specific malaria control measures. We analyzed the genetic diversity and population structure of 425 P. vivax isolates from Sri Lanka, Myanmar, and Ethiopia using 12 trinucleotide and tetranucleotide microsatellite markers. All three parasite populations were highly polymorphic with 3–44 alleles per locus. Approximately 65% were multiple-clone infections. Mean genetic diversity ( H E ) was 0.7517 in Ethiopia, 0.8450 in Myanmar, and 0.8610 in Sri Lanka. Significant linkage disequilibrium was maintained. Population structure showed two clusters (Asian and African) according to geography and ancestry. Strong clustering of outbreak isolates from Sri Lanka and Ethiopia was observed. Predictive power of ancestry using two-thirds of the isolates as a model identified 78.2% of isolates accurately as being African or Asian. Microsatellite analysis is a useful tool for mapping short-term outbreaks of malaria and for predicting ancestry.
8 Schousboe, M. L.; Rajakaruna, R. S.; Amerasinghe, Priyanie.; Konradsen, F.; Ord, R.; Pearce, R.; Bygbjerg, C.; Roper, C.; Alifrangis, M. 2011. Analysis of polymorphisms in the merozoite surface protein-3a gene and two microsatellite loci in Sri Lankan Plasmodium vivax: evidence of population substructure in Sri Lanka. American Journal of Tropical Medicine and Hygiene, 85(6):994-1001. [doi: https://doi.org/10.4269/ajtmh.2011.11-0338]
Malaria ; Plasmodium vivax ; Population ; Public health ; Polymorphism ; Satellite surveys ; Statistical methods ; Genetic variation / Sri Lanka
(Location: IWMI HQ Call no: e-copy only Record No: H044603)
(0.59 MB)
The geographical distribution of genetic variation in Plasmodium vivax samples ( N = 386) from nine districts across Sri Lanka is described using three markers; the P. vivax merozoite surface protein -3a ( Pvmsp -3a) gene, and the two microsatellites m1501 and m3502. At Pvmsp -3a, 11 alleles were found with an expected heterozygosity (H e ) of 0.81, whereas at m1501 and m3502, 24 alleles (H e = 0.85) and 8 alleles (H e = 0.74) were detected, respectively. Overall, 95 unique three locus genotypes were detected among the 279 samples positive at all three loci (H e = 0.95). Calculating the pairwise fixation index ( F ST ) revealed statistically significant population structure. The presence of identical 2-loci microsatellite genotypes in a significant proportion of samples revealed local clusters of closely related isolates contributing to strong linkage disequilibrium between marker alleles. The results show evidence of high genetic diversity and possible population substructure of P. vivax populations in Sri Lanka.
9 Jayawardena, U. A.; Tkach, V. V.; Navaratne, A. N.; Amerasinghe, Priyanie H.; Rajakaruna, R. S.. 2013. Malformations and mortality in the Asian common toad induced by exposure to Pleurolophocercous cercariae (Trematoda: Cryptogonimidae). Parasitology International, 62:246-252. [doi: https://doi.org/10.1016/j.parint.2013.01.003]
(Location: IWMI HQ Call no: e-copy only Record No: H046260)
(0.58 MB)
Malformations and increased mortality due to infection by the digenetic trematode, Riberioa ondatrae have been reported for many species of amphibians. Severe malformations have also been reported in the Common Hourglass Tree Frog, Polypedates cruciger induced by Pleurolophocercous cercariae in Sri Lanka in addition to the changes in the behaviour, development and survival of the host. We exposed pre-limb bud stage tadpoles (Gosner stages 25–26) of the Asian Common Toad, Duttaphrynus melanostictus to the same pleurolophocercous type cercariae under laboratory conditions. Molecular and morphological identification showed that these cercariae belonged Acanthostomum burminis infecting freshwater snakes as definitive hosts. These cercariae induced malformations (27.8%) and reduced survival to metamorphosis (53.8%). The magnitude of the effects increased with the dose of cercariae. Types of malformations were mainly axial, such as scoliosis and kyphosis. Severe limb malformations such as extra or missing limbs as reported for amphibians exposed to R. ondatrae were not observed in the D. melanostictus. Same authors reported a higher percentage of malformations previously when P. cruciger was exposed to the cercariae A. burminis compared to D. melanostictus. However, tadpoles of D. melanostictus, which are smaller compared to those of P. cruciger, experienced higher mortality than P. cruciger tadpoles. Trematode induced malformations and mortality in amphibians are highly variable and depend on multiple factors such as host species differences such as resistance to infection and tolerance, life-history characteristics such as size at metamorphosis and length of the metamorphosis period, and other factors such as size of the amphibian at the time of trematode exposure.
10 Schousboe, M. L.; Ranjitkar, S.; Rajakaruna, R. S.; Amerasinghe, Priyanie; Konradsen, F.; Morales, F.; Ord, R.; Pearce, R.; Leslie, T.; Rowland, M.; Gadalla, N; Bygbjerg, C.; Alifrangis, M.; Roper, C. 2014. Global and local genetic diversity at two microsatellite loci in Plasmodium vivax parasites from Asia, Africa and South America. Malaria Journal, 13:1-9. [doi: https://doi.org/10.1186/1475-2875-13-392]
Genetic variation ; Plasmodium vivax ; Parasites ; Loci ; Malaria ; Public health ; Microsatellites / Asia / Africa / South America / Sri Lanka / Pakistan / Afghanistan / Nepal / Sudan / Venezuela / Ecuador
(Location: IWMI HQ Call no: e-copy only Record No: H047016)
http://www.malariajournal.com/content/pdf/1475-2875-13-392.pdf
https://vlibrary.iwmi.org/pdf/H047016.pdf
https://vlibrary.iwmi.org/pdf/H047016.pdf
(0.34 MB) (349 KB)
Background: Even though Plasmodium vivax has the widest worldwide distribution of the human malaria species and imposes a serious impact on global public health, the investigation of genetic diversity in this species has been limited in comparison to Plasmodium falciparum. Markers of genetic diversity are vital to the evaluation of drug and vaccine efficacy, tracking of P. vivax outbreaks, and assessing geographical differentiation between parasite populations.
Methods: The genetic diversity of eight P. vivax populations (n = 543) was investigated by using two microsatellites (MS), m1501 and m3502, chosen because of their seven and eight base-pair (bp) repeat lengths, respectively. These were compared with published data of the same loci from six other P. vivax populations.
Results: In total, 1,440 P. vivax samples from 14 countries on three continents were compared. There was highest heterozygosity within Asian populations, where expected heterozygosity (He) was 0.92-0.98, and alleles with a high repeat number were more common. Pairwise FST revealed significant differentiation between most P. vivax populations, with the highest divergence found between Asian and South American populations, yet the majority of the diversity (~89%) was found to exist within rather than between populations.
Conclusions: The MS markers used were informative in both global and local P. vivax population comparisons and their seven and eight bp repeat length facilitated population comparison using data from independent studies. A complex spatial pattern of MS polymorphisms among global P. vivax populations was observed which has potential utility in future epidemiological studies of the P. vivax parasite.
Methods: The genetic diversity of eight P. vivax populations (n = 543) was investigated by using two microsatellites (MS), m1501 and m3502, chosen because of their seven and eight base-pair (bp) repeat lengths, respectively. These were compared with published data of the same loci from six other P. vivax populations.
Results: In total, 1,440 P. vivax samples from 14 countries on three continents were compared. There was highest heterozygosity within Asian populations, where expected heterozygosity (He) was 0.92-0.98, and alleles with a high repeat number were more common. Pairwise FST revealed significant differentiation between most P. vivax populations, with the highest divergence found between Asian and South American populations, yet the majority of the diversity (~89%) was found to exist within rather than between populations.
Conclusions: The MS markers used were informative in both global and local P. vivax population comparisons and their seven and eight bp repeat length facilitated population comparison using data from independent studies. A complex spatial pattern of MS polymorphisms among global P. vivax populations was observed which has potential utility in future epidemiological studies of the P. vivax parasite.
11 Schousboe, M. L.; Ranjitkar, S.; Rajakaruna, R. S.; Amerasinghe, Priyanie H.; Morales, F.; Pearce, R.; Ord, R.; Leslie, T.; Rowland, M.; Gadalla, N. B.; Konradsen, F.; Bygbjerg, C.; Roper, C.; Alifrangis, M. 2015. Multiple origins of mutations in the mdr1 gene—a putative marker of chloroquine resistance in P. vivax. PLoS Neglected Tropical Diseases, 9(11):1-17. [doi: https://doi.org/10.1371/journal.pntd.0004196]
Medical sciences ; Mutation ; Malaria ; Drugs ; Codons ; Genes ; DNA ; Microsatellites / Pakistan / Afghanistan / Sri Lanka / Nepal / Sudan / Sao Tome / Ecuador
(Location: IWMI HQ Call no: e-copy only Record No: H047288)
http://www.plosntds.org/article/fetchObject.action?uri=info:doi/10.1371/journal.pntd.0004196&representation=PDF
https://vlibrary.iwmi.org/pdf/H047288.pdf
https://vlibrary.iwmi.org/pdf/H047288.pdf
(1.19 MB) (1.19 MB)
Background
Chloroquine combined with primaquine has been the ecommended antimalarial treatment of Plasmodium vivax malaria infections for six decades but the efficacy of this treatment regimen is threatened by chloroquine resistance (CQR). Single nucleotide polymorphisms (SNPs) in the multidrug resistance gene, Pvmdr1 are putative determinants of CQR but the extent of their emergence at population level remains to be explored.
Objective
In this study we describe the prevalence of SNPs in the Pvmdr1 among samples collected in seven P. vivax endemic countries and we looked for molecular evidence of drug selection by characterising polymorphism at microsatellite (MS) loci flanking the Pvmdr1 gene.
Methods
We examined the prevalence of SNPs in the Pvmdr1 gene among 267 samples collected from Pakistan, Afghanistan, Sri Lanka, Nepal, Sudan, Sao Tome and Ecuador. We measured and diversity in four microsatellite (MS) markers flanking the Pvmdr1 gene to look evidence of selection on mutant alleles.
Results
SNP polymorphism in the Pvmdr1 gene was largely confined to codons T958M, Y976F and F1076L. Only 2.4% of samples were wildtype at all three codons (TYF, n = 5), 13.3% (n =28) of the samples were single mutant MYF, 63.0% of samples (n = 133) were double mutant MYL, and 21.3%(n = 45) were triple mutant MFL. Clear geographic differences in the prevalence of these Pvmdr mutation combinations were observed. Significant linkage disequilibrium (LD) between Pvmdr1 and MS alleles was found in populations sampled in Ecuador, Nepal and Sri Lanka, while significant LD between Pvmdr1 and the combined 4 MS locus haplotype was only seen in Ecuador and Sri Lanka. When combining the 5 loci, high level diversity, measured as expected heterozygosity (He), was seen in the complete sample set (He = 0.99), while He estimates for individual loci ranged from 0.00–0.93. Although Pvmdr1 haplotypes were not consistently associated with specific flanking MS alleles, there was significant differentiation between geographic sites which could indicate directional selection through local drug pressure.
Conclusions
Our observations suggest that Pvmdr1 mutations emerged independently on multiple occasions even within the same population. In Sri Lanka population analysis at multiple sites showed evidence of local selection and geographical dispersal of Pvmdr1 mutations between sites.
Chloroquine combined with primaquine has been the ecommended antimalarial treatment of Plasmodium vivax malaria infections for six decades but the efficacy of this treatment regimen is threatened by chloroquine resistance (CQR). Single nucleotide polymorphisms (SNPs) in the multidrug resistance gene, Pvmdr1 are putative determinants of CQR but the extent of their emergence at population level remains to be explored.
Objective
In this study we describe the prevalence of SNPs in the Pvmdr1 among samples collected in seven P. vivax endemic countries and we looked for molecular evidence of drug selection by characterising polymorphism at microsatellite (MS) loci flanking the Pvmdr1 gene.
Methods
We examined the prevalence of SNPs in the Pvmdr1 gene among 267 samples collected from Pakistan, Afghanistan, Sri Lanka, Nepal, Sudan, Sao Tome and Ecuador. We measured and diversity in four microsatellite (MS) markers flanking the Pvmdr1 gene to look evidence of selection on mutant alleles.
Results
SNP polymorphism in the Pvmdr1 gene was largely confined to codons T958M, Y976F and F1076L. Only 2.4% of samples were wildtype at all three codons (TYF, n = 5), 13.3% (n =28) of the samples were single mutant MYF, 63.0% of samples (n = 133) were double mutant MYL, and 21.3%(n = 45) were triple mutant MFL. Clear geographic differences in the prevalence of these Pvmdr mutation combinations were observed. Significant linkage disequilibrium (LD) between Pvmdr1 and MS alleles was found in populations sampled in Ecuador, Nepal and Sri Lanka, while significant LD between Pvmdr1 and the combined 4 MS locus haplotype was only seen in Ecuador and Sri Lanka. When combining the 5 loci, high level diversity, measured as expected heterozygosity (He), was seen in the complete sample set (He = 0.99), while He estimates for individual loci ranged from 0.00–0.93. Although Pvmdr1 haplotypes were not consistently associated with specific flanking MS alleles, there was significant differentiation between geographic sites which could indicate directional selection through local drug pressure.
Conclusions
Our observations suggest that Pvmdr1 mutations emerged independently on multiple occasions even within the same population. In Sri Lanka population analysis at multiple sites showed evidence of local selection and geographical dispersal of Pvmdr1 mutations between sites.
12 Ariyarathne, S.; Apanaskevich, D. A.; Amerasinghe, Priyanie H.; Rajakaruna, R. S.. 2016. Diversity and distribution of tick species (Acari: Ixodidae) associated with human otoacariasis and socio-ecological risk factors of tick infestations in Sri Lanka. Experimental And Applied Acarology, 70(1):99-123. [doi: https://doi.org/10.1007/s10493-016-0056-z]
Biodiversity ; Ixodidae ; Ecology ; Infestation ; Tickborne diseases ; Risk factors ; Health hazards ; Domestic animals / Sri Lanka / Anuradhapura / Kandy / Kurunegala / Nuwara Eliya / Ratnapura
(Location: IWMI HQ Call no: e-copy only Record No: H048100)
Tick infestation in humans is a major public health concern. The diversity and distribution of tick species associated with human otoacariasis was studied in five districts: Anuradhapura, Kandy, Kurunegala, Nuwara Eliya and Ratnapura in the main agro-climatic zones of Sri Lanka. Ticks from patients attending the ear, nose and throat clinics of the General Hospitals were collected during a 3 year period. In total 426 ticks were collected. Most human otoacariasis cases were reported from Kandy (33.8 %) and the fewest from Nuwara Eliya (8.2 %). Of the five tick species identified, nymphs of Dermacentor auratus constituted 90.6 % of the collection. Rhipicephalus sanguineus, Hyalomma isaaci, Haemaphysalis bispinosa and Otobius megnini were found rarely infesting humans possibly as an accidental host; H. bispinosa and O. megnini in the human ear canal were first time records in Sri Lanka. Females and children under 10 years were identified as risk groups of human otoacariasis. Subsequently, a field study was carried out to determine socio-ecological risk factors of human tick infestations in the five districts. Based on hospital data, eight villages with high prevalence of otoacariasis were selected from each district. A total 40 villages were visited and 1674 household members were interviewed. Involvement in outdoor activities, presence of wild animals around the house, location of the house in close proximity to a forest and occupation were identified as major risk factors.
13 Jayawardena, U. A.; Rohr, J. R.; Navaratne, A. N.; Amerasinghe, Priyanie H.; Rajakaruna, R. S.. 2016. Combined effects of pesticides and trematode infections on hourglass tree frog Polypedates cruciger. Ecohealth, 13(1):111-22. [doi: https://doi.org/10.1007/s10393-016-1103-2]
Pesticides ; Trematode infections ; Frogs ; Glyphosate ; Chlorpyrifos ; Dimethoate ; Malformations ; Propanil ; Environmental factors ; Chemical contamination ; Disease prevention ; Infectious diseases ; Mathematical models
(Location: IWMI HQ Call no: e-copy only Record No: H048101)
The impact of widespread and common environmental factors, such as chemical contaminants, on infectious disease risk in amphibians is particularly important because both chemical contaminants and infectious disease have been implicated in worldwide amphibian declines. Here we report on the lone and combined effects of exposure to parasitic cercariae (larval stage) of the digenetic trematode, Acanthostomum burminis, and four commonly used pesticides (insecticides: chlorpyrifos, dimethoate; herbicides: glyphosate, propanil) at ecologically relevant concentrations on the survival, growth, and development of the common hourglass tree frog, Polypedates cruciger Blyth 1852. There was no evidence of any pesticide-induced mortality on cercariae because all the cercariae successfully penetrated each tadpole host regardless of pesticide treatment. In isolation, both cercarial and pesticide exposure significantly decreased frog survival, development, and growth, and increased developmental malformations, such as scoliosis, kyphosis, and also edema and skin ulcers. The combination of cercariae and pesticides generally posed greater risk to frogs than either factor alone by decreasing survival or growth or increasing time to metamorphosis or malformations. The exception was that lone exposure to chlorpyrifos had higher mortality without than with cercariae. Consistent with mathematical models that suggest that stress should increase the impact of generalist parasites, the weight of the evidence from the field and laboratory suggests that ecologically relevant concentrations of agrochemicals generally increase the threat that trematodes pose to amphibians, highlighting the importance of elucidating interactions between anthropogenic activities and infectious disease in taxa of conservation concern.
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