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Relevance of improved epidemiological knowledge to sustainable control of Haemonchus contortus in Nigeria

Published online by Cambridge University Press:  20 November 2012

M. B. Bolajoko*
Affiliation:
School of Biological Sciences, University of Bristol, Woodland Road, Bristol, BS8 1UG, UK Epidemiology Unit, National Veterinary Research Institute, Vom, Plateau State, Nigeria
E. R. Morgan
Affiliation:
School of Biological Sciences, University of Bristol, Woodland Road, Bristol, BS8 1UG, UK
*
*Corresponding author. E-mail: [email protected]

Abstract

Nigeria experiences losses in small ruminant production as a result of a high prevalence of infection with Haemonchus contortus, but there have been very few investigative studies into the epidemiology of H. contortus in Nigeria, particularly in the south and western parts of the country. For successful planning and execution of control of hemonchosis in Nigeria, there is a need for insight into the epidemiology of free-living stages under the prevailing local conditions and models for climatic and environmental factors that control the risk of hemonchosis and distribution of H. contortus. In this review, we assess previous studies on the epidemiology of H. contortus in Nigeria, evaluate the present climatic and epidemiological situation, and highlight areas that require further investigative studies. The goal is to identify factors that underpin better control strategies and holistic integrated farm-management practice. Previous studies on H. contortus provided important information for formulation of control strategies and development toward integrated parasite management. However, this review has revealed the need for holistic evaluation of the current epidemiology and prevalence of H. contortus in Nigeria, particularly in relation to climate change. Accurate information is needed to build useful predictive models of the population dynamics of all free-living stages, particularly the L3.

Type
Review Article
Copyright
Copyright © Cambridge University Press 2012

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References

Agyei, AD (1997). Seasonal changes in the level of infective strongyle nematodes larvae on pasture in the costal savannah regions of Ghana. Veterinary Parasitology 70: 175182.CrossRefGoogle Scholar
Altaif, KI and Yakoob, AY (1987). Development and survival of Haemonchus contortus larvae on pasture in Iraq. Tropical Animal Health and Production 19: 8892.CrossRefGoogle ScholarPubMed
Anderson, RM and May, RM (1991). Infectious Diseases of Humans: Dynamics and Control. Oxford, UK: Oxford University Press.CrossRefGoogle Scholar
Aspin, M (1999). Breeding sheep with resistance to nematode infection [online]. Meat New Zealand R&D Brief 34. Available online at http://www.beeflambnz.com/Documents/Farm/Breeding%20sheep%20with%20resistance%20to%20nematode%20infection.pdf Last accessed September 14, 2012.Google Scholar
Ayalew, L and Gibbs, HC (1973). Seasonal fluctuations of nematode populations in breeding ewes and lambs. Canadian Journal of Comparative Medicine 37: 7989.Google ScholarPubMed
Ayinde, OE, Muchie, M and Olatunji, GB (2011). Effect of climate change on agricultural productivity in Nigeria: a co-integration model approach. Journal of Human Ecology 35: 189194.CrossRefGoogle Scholar
Barger, IA (1997). Control by management. Veterinary Parasitology 72: 493506.CrossRefGoogle ScholarPubMed
Barger, IA (1999). The role of epidemiological knowledge and grazing management for helminth control in small ruminants. International Journal of Parasitology 29: 4147.CrossRefGoogle ScholarPubMed
Barger, IA, Benyon, PR and Southcott, WH (1972). Simulation of pasture larval populations of Haemonchus contortus.Google Scholar
Bath, GF, Hansen, JW, Krecek, RC, van Wyk, JA and Vatta, AF (2001). Sustainable Approaches for Managing Haemonchosis in Sheep and Goats: Final Report of Food and Agriculture Organization (FAO) Technical Co-operation Project no. TCP/SAF/8821(A).Google Scholar
Bishop, SC and Stear, MJ (2003). Modelling of host genetics and resistance to infectious diseases: understanding and controlling nematode infections. Veterinary Parasitology 115: 147166.CrossRefGoogle ScholarPubMed
Bishop, SC, Bairden, K, McKellar, QA and Stear, MJ (1996). Genetic parameters for faecal egg count following mixed, natural predominantly Ostertagia circumcincta infection and relationships with live weight in young lambs. Animal Science 63: 423428.CrossRefGoogle Scholar
Bolajoko, MB (2002). The pathologic effects of haemonchosis on the abomasums of sheep slaughtered in the Sokoto central abattoir, Sokoto State, Nigeria. DVM Thesis. Usmanu Danfodiyo University, Sokoto, Sokoto State, Nigeria.Google Scholar
Brooks, CEP (1916). The rainfall of Nigeria and the Gold Coast. Quarterly Journal of the Royal Meteorological Society 42: 85106.Google Scholar
Brooks, CEP (1920a). The distribution of temperature over Nigeria. Quarterly Journal of the Royal Meteorological Society 46: 204214.Google Scholar
Brooks, CEP (1920b). Distribution of relative humidity over Nigeria. Quarterly Journal of the Royal Meteorological Society 46: 289292.CrossRefGoogle Scholar
Burke, J (2005). Management of Barber pole worm in sheep and goats in the southern U.S. Small Farm Research Update. [Available online at https://attra.ncat.org/downloads/goat_barber_pole.pdf Last accessed September 14, 2012].Google Scholar
Capitini, LA, McClure, KE and Herd, RP (1990). Effect of environmental stimuli on pre-infective and infective stages of Haemonchus contortus in northern United States for the induction of hypobiosis. Veterinary Parasitology 35: 281293.CrossRefGoogle ScholarPubMed
Callinan, APL and Westcott, JM (1986). Vertical distribution of trichostrongylid larvae on herbage and in soil. International Journal of Parasitology 16: 241244.CrossRefGoogle ScholarPubMed
Chandrawathani, P, Jamnah, O, Waller, PJ, Larsen, M, Gillespie, A and Zahari, WM (2003). Biological control of nematode parasites of small ruminants in Malaysia using the nematophagous fungus Duddingtonia flagrans. Veterinary Parasitology 117: 173183.CrossRefGoogle ScholarPubMed
Chandrawathani, P, Jamnah, O, Waller, PJ, Larsen, M and Gillespie, AT (2004). Field studies on the biological control of nematode parasites of sheep in the tropics, using the microfungus Duddingtonia flagrans. Veterinary Parasitology 120: 177187.CrossRefGoogle ScholarPubMed
Chaudary, FR, Qayyum, M and Miller, JE (2008). Development and survival of Haemonchus contortus infective larvae derived from sheep faeces under sub-tropical conditions in the Potohar region of Pakistan. Tropical Animal Health and Production 40: 8592.CrossRefGoogle ScholarPubMed
Chiejina, SN (1986). The epizootiology and control of parasitic gastro-enteritis of domesticated ruminants in Nigeria. Helminthological Abstracts (Series A) 55: 413429.Google Scholar
Chiejina, SN and Emehelu, CO (1984). Seasonal changes in pasture populations of infective larvae of gastrointestinal nematodes of cattle in eastern Nigeria. Research in Veterinary Science 37: 144147.Google ScholarPubMed
Chiejina, SN and Fakae, BB (1984). Development and survival of infective larvae of gastrointestinal nematode parasites of cattle in eastern Nigeria. Research in Veterinary Science 37: 148153.Google ScholarPubMed
Chiejina, SN and Fakae, BB (1989). The ecology of infective larvae of bovine gastrointestinal trichostrongylids in dry season contaminated pastures in the Nigerian derived savannah. Journal of Helminthology 63: 127139.CrossRefGoogle Scholar
Chiejina, SN, Fakae, BB and Eze, BO (1988). Arrested development of gastrointestinal trichostrongylids in goats in Nigeria. Veterinary Parasitology 28: 103113.CrossRefGoogle ScholarPubMed
Chiejina, SN, Fakae, BB and Eze, PI (1989). Development and survival of free-living stages of gastrointestinal nematodes of sheep and goats on pasture in the Nigerian derived savannah. Veterinary Research Communication 13: 103112.CrossRefGoogle Scholar
Crofton, HD (1948). The ecology of immature phases of trichostrongyle nematodes. Parasitology 39: 1725.CrossRefGoogle ScholarPubMed
Crofton, HD (1963). Nematode parasite populations in sheep and on pasture. Technical communications No. 35 of the Commonwealth Bureau of Helminthology, St. Albans, P19. Commonwealth Bureau, Farnham Royal, Buckinghamshire, England.Google Scholar
Crofton, HD (1965). Ecology and biological plasticity of sheep nematodes. I. The effect of temperature on the hatching of eggs of some nematode parasites of sheep. Cornell Veterinarian 55: 259262.Google ScholarPubMed
Connan, RM (1975). Inhibited development in Haemonchus contortus. Parasitology 71: 239246.CrossRefGoogle ScholarPubMed
Cornell, S (2005). Modelling nematode populations: 20 years of progress. Trends in Parasitology 21: 542545.CrossRefGoogle ScholarPubMed
Dinaburg, AG (1944). Development and survival under outdoor conditions of eggs and larvae of the common ruminant stomach worm, Haemonchus contortus. Journal of Agricultural Research 69: 421433.Google Scholar
Dinnik, JA and Dinnik, NN (1958). Observations on the development of Haemonchus contortus larvae under field conditions in the Kenya Highland. Bulletin of Epizootic Diseases of Africa 6: 1121.Google Scholar
Dinnik, JA and Dinnik, NN (1961). Observations on the longevity of Haemonchus contortus larvae on pasture herbage in the Kenya Highlands. Bulletin of Epizootics Diseases of Africa 9: 193208.Google Scholar
Dobson, RJ, Donald, AD, Barnes, EH and Waller, PJ (1990). Population dynamics of trichostrongylus colubriformis in sheep: model to predict the worm population over time as function of infection rate and host age. International Journal of Parasitology 20: 347352.Google ScholarPubMed
Dunn, AM (1978). Veterinary Helminthology, 2nd ed.London: William Heinemann Medical Books, pp. 172195.Google Scholar
Fabiyi, JP (1973). Seasonal fluctuations of nematode infestations in goats in the savannah belt of Nigeria. Bulletin of Epizootic Diseases in Africa 21: 277285.Google Scholar
Fakae, BB (1990a). Seasonal changes and hypobiosis in Haemonchus contortus Infection in the West African dwarf sheep and goats in the Nigerian derived savannah. Veterinary Parasitology 36: 123130.CrossRefGoogle Scholar
Fakae, BB (1990b). The epidemiology of helminthiasis in small ruminants under the traditional husbandry system in eastern Nigeria. Veterinary Research Communication 14: 381391.Google Scholar
Fakae, BB and Chiejina, SN (1988). Relative contributions of late dry-season and early rains pasture contaminations with trichostrongyle eggs to the wet-season herbage infestation in Eastern Nigeria. Veterinary Parasitology 28: 115123.CrossRefGoogle Scholar
Gatongi, PM, Scott, ME, Ranjan, S, Gathuma, JM, Munya, WK, Cheruiyot, H and Prichard, RK (1997). Effects of three nematode anthelmintic treatment regimes on flock performance of sheep and goats under extensive management in semi-arid Kenya. Veterinary Parasitology 68: 323336.Google ScholarPubMed
Gettinby, G and Paton, G (1981). The role of temperature in predicting the pattern of bovine Ostertagia infection on pasture. Journal of Theoretical Biology 6: 395402.Google Scholar
Gibson, TE and Everett, G (1976). The ecology of the free-living stages of Haemonchus contortus. British Veterinary Journal 132: 5059.CrossRefGoogle ScholarPubMed
Githigia, SM, Thamsborg, SM and Larsen, M (2001). Effectiveness of grazing management in controlling gastrointestinal nematodes in weaner lambs on pasture in Denmark. Veterinary Parasitology 99: 1527.CrossRefGoogle ScholarPubMed
Gordon, HM (1948). Epidemiology of parasitic diseases, with special reference to studies with nematode parasites of sheep. Australian Veterinary Journal 24: 1745.CrossRefGoogle Scholar
Gordon, HM (1953). The epidemiology of helminthosis in sheep in winter rainfall regions of Australia. I. Preliminary observations. Australian Veterinary Journal 39: 337348.CrossRefGoogle Scholar
Gray, GD (1997). The use of genetically resistant sheep to control nematode parasitism. Veterinary Parasitology 72: 345366.CrossRefGoogle ScholarPubMed
Griffin, L (1984). Strategic deworming programs in ruminant. Onderstepoort Journal of Veterinary Research 54: 41.Google Scholar
Gronvold, J, Henriksen, SA, Larsen, M, Nansen, P and Wolstrup, J (1996). Biological control: aspects of biological control – with special reference to arthropods, protozoans and helminths of domesticated animals. Veterinary Parasitology 64: 4764.Google Scholar
Herd, RP, Streitel, RH, McClure, KE and Parker, CF (1984). Control of hypobiotic and benzimidazole-resistant nematodes of sheep. Journal of the American Veterinary. Medical Association 184: 726730.Google Scholar
Jimoh, OD and Ayodeji, OS (2003). Impact of the Gurara River (Nigeria) interbasin water transfer scheme on the Kaduna River at the Shiroro Dam. Water Resources Systems—Hydrological Risk, Management and Development (Proceedings of Symposium HS02b held during 1UGG2003 at Sapporo. July 2003). IAHS Publ. no. 281. 2003. 277286.Google Scholar
Karin, C (2004). The Biology of Goat. [Available fromhttp://www.goatbiology.com/parasites.html Last accessed September 19, 2012].Google Scholar
Keeling, MJ and Rohani, P (2008). Modelling Infectious Diseases in Humans and Animals. Princeton, NJ and Oxford: Princeton University Press.Google Scholar
Kenyon, F and Greer, AW, Coles, GC, Cringoli, G, Papadopoulos, E and Cabaret, J (2009). The role of targeted selective treatments in the development of refugia-based approaches to the control of gastrointestinal nematodes of small ruminants. Veterinary Parasitology 164: 311.CrossRefGoogle Scholar
Larsen, M (2006). Biological control of nematode parasites in sheep. Journal of Animal Science 84: E133E139.CrossRefGoogle ScholarPubMed
Larsen, M, Wolstrup, J, Henriksen, Sv Aa, Dackman, C, Grønvold, J and Nansen, P (1991). In vitro stress selection of nematophagus fungi for bio-control of pre-parasitic nematode larvae of ruminants. Journal of Helminthology 65: 193200.CrossRefGoogle Scholar
Larsen, M, Faedo, M, Waller, PJ and Hennessy, DR (1998). The potential of nematophagous fungi to control the free-living stages of nematode parasites of sheep: studies with Duddingtonia flagrans. Veterinary Parasitology 76: 121128.CrossRefGoogle ScholarPubMed
Lee, RP, Armour, J and Ross, JG (1960). The seasonal variations of strongyle infestations in Nigerian zebu cattle. British Veterinary Journal 116: 3446.CrossRefGoogle Scholar
May, RM (1977). Dynamical aspects of host-parasite associations: Croften's model revisited. Parasitology 75: 259275.CrossRefGoogle Scholar
Michel, JF (1969). The epidemiology and control of some nematode infections of grazing animals. Advances in Parasitology 7: 211282.CrossRefGoogle ScholarPubMed
Misra, SC and Ruprah, NS (1972). Vertical migration of Haemonchus contortus infective larvae on experimental grass pots. Indian Journal of Animal Science 42: 843846.Google Scholar
Morgan, ER, Milner-Gulland, EJ, Torgerson, PR and Medley, GF (2004). Ruminating on complexity: macroparasites of wildlife and lifestock. TRENDS in Ecology and Evolution 19 (4): 181188.CrossRefGoogle Scholar
Morgan, ER and Wall, R (2009). Climate change and parasitic disease: farmer mitigation? Trends in Parasitology 25: 308313.CrossRefGoogle ScholarPubMed
Morgan, ER, Medley, GF, Torgerson, PR, Shaikenov, BS and Milner-Gulland, EJ (2006). Parasite transmission in a migratory multiple host system. Ecological Modelling 200: 511520.CrossRefGoogle Scholar
Nardone, A, Ronchi, B, Lacetera, N, Ranieri, MS and Bernabucci, U (2010). Effects of climate changes on animal production and sustainability of livestock systems. Livestock Science 130: 5769.CrossRefGoogle Scholar
Niezen, JH, Robertson, HA, Waghorn, GC and Charleston, WAG (1998). Production, faecal egg counts and worm burdens of ewe lambs which grazed six contrasting forages. Veterinary Parasitology 80: 1527.Google Scholar
Nwosu, CO (1995). Helminth parasites of captive wild animals in Borno State of Nigeria. Tropical Veterinarian 13: 5964.Google Scholar
Nwosu, CO, Ogunrinade, AF and Fagbemi, BO (1996). The seasonal prevalence of Haemonchus species in Red Sokoto (Maradi) goats in Nigeria. Veterinary Research Communications 20: 367370.Google Scholar
O'Connor, LJ, Walkden-Brown, SW and Kahn, LP (2006). Ecology of the free-living stages of major trichostrongylid parasites of sheep. Veterinary Parasitology 142: 115.CrossRefGoogle ScholarPubMed
Ogunsusi, RA and Eysker, M (1979). Inhibited development of trichostrongylids of sheep in northern Nigeria. Research in Veterinary Science 26: 108110.CrossRefGoogle ScholarPubMed
Okon, ED and Akinpelu, AI (1982). Development and survival of nematode larvae on pasture in Calabar, Nigeria. Tropical Animal Health and Production 14: 2325.CrossRefGoogle ScholarPubMed
Okon, ED and Enyenihi, UK (1977). Development and survival of Haemonchus contortus larvae on pastures in Ibadan. Tropical Animal Health and Production 9: 710.CrossRefGoogle ScholarPubMed
Onyali, IO, Onwuliri, COE and Ajayi, JA (1990). Development and survival of Haemonchus contortus larvae on pasture at Vom, Plateau State, Nigeria. Veterinary Research Communications 14: 211216.CrossRefGoogle ScholarPubMed
Paton, G, Thomas, RJ and Waller, PJ (1984). A prediction model for parasitic gastro-enteritis in lambs. International Journal of Parasitology 14: 439445.Google Scholar
Patz, JA, Confalonieri, UEC, Amerasinghe, FP, Chua, KB, Daszak, P, Hyatt, AD, Molyneux, D, Thomson, M, Yameogo, L, Lazaro, MM, Vasconcelos, P, Rubio-Palis, Y, Campbell-Lendrum, D, Jaenisch, T, Mahamat, H, Mutero, C, Waltner-Toews, D and Whiteman, C, (2005). Human health: ecosystem regulation of infectious diseases. In: Ecosystems and Human Well-Being. Current State and Trends, vol. 1. The Millennium Ecosystem Assessment. [Available from http://www.millenniumassessment.org/documents/document.357.aspx.pdf Last accessed September 14, 2012].Google Scholar
Peña, MT, Miller, JE, Fontenot, ME, Gillespie, A and Larsen, M (2002). Evaluation of Duddingtonia flagrans in reducing infective larvae of Haemonchus contortus in faeces of sheep. Veterinary Parasitology 103: 259265.CrossRefGoogle ScholarPubMed
Rahmann, G and Seip, H (2006). Alternative management strategies to prevent and control endo-parasite diseases in sheep and goat farming systems – a review of the recent scientific knowledge Landbauforschung Völkenrode 2, 193206.Google Scholar
Rees, G (1950). Observations on the vertical migrations of the third-stage larva of Haemonchus contortus (Rud) on experimental plots of Lilium perenne S24, in relation to meteorological and micrometeorological factors. Parasitology 40: 127143.CrossRefGoogle Scholar
Roberts, M and Heesterbeek, J (1993). Bluff your way in epidemiological models. Trends in Microbiology 1: 343348.CrossRefGoogle Scholar
Rolfe, PF (1990). Chemical resistance in livestock – an overview. In: Weeds and Worms: Combat Resistance – Proceedings of the Riverina Outlook Conference 1990, Wagga Wagga, NSW, Australia.Google Scholar
Rose, JH (1963). Observations on the free-living stages of the stomach worm Haemonchus contortus. Parasitology 53: 469481.CrossRefGoogle Scholar
Secher, B, Gronvold, J and Thamsborg, S (1992). Unpublished data. In: Thamsborg SM, Jörgensen SM, Waller PJ, Nansen P, 1996. The influence of stocking rate on gastrointestinal nematode infections of sheep over a 2-year grazing period. Veterinary Parasitology 67: 207224.Google Scholar
Schillhorn Van Veen, TW (1973). Small ruminant health problems in Northern Nigeria with emphasis on helminthosis. Nigerian Veterinary Journal 2: 2631.Google Scholar
Schillhorn Van Veen, TW (1978). Haemonchosis in sheep during the dry season in the Nigerian savannah. Veterinary Record 102: 364365.Google Scholar
Schad, GA (1977). The role of arrested development in the regulation of nematode populations. In: Esch, GW (ed) Regulation of parasite populations. Proceedings of Symposium Sponsored by American Societyfor Microbiology and American Society for Parasitology, New Orleans, 10–14 November, 1975. London: Academic Press, pp. 111167.Google Scholar
Schoenian, S (2005). Internal parasite control [online]. [Available from www.sheep101.info/201/parasite.html Last accessed September 14, 2012].Google Scholar
Shorb, DA (1944). Factors influencing embryonation and survival of eggs of the stomach worm, Haemonchus contortus. Journal of Agricultural Research 69: 279287.Google Scholar
Silangwa, SM and Todd, AC (1964). Vertical migration of Trichostronggylid larvae on grasses. Journal of Parasitology 50: 278285.CrossRefGoogle ScholarPubMed
Silva, BF, Amarante, MRV, Kadri, SM, Carrijio-Mauad, JR and Amarante, AFT (2008). Vertical migration of Haemonchus contortus third stage larvae on Brachiaria decumbens grass. Veterinary Parasitology 158: 8592.CrossRefGoogle ScholarPubMed
Silverman, PH and Campbell, JA (1959). Studies on parasitic worms of sheep in Scotland. I. Embryonic and larval development of Haemonchus contortus at constant conditions. Parasitology 49: 2328.CrossRefGoogle ScholarPubMed
Sissay, MM, Uggla, A and Waller, PJ (2007). Epidemiology and seasonal dynamics of gastrointestinal nematode infections of sheep in a semi-arid region of eastern Ethiopia. Veterinary Parasitology 143: 311321.Google Scholar
Skinner, WD and Todd, KS Jr. (1980). Lateral migration of Haemonchus contortus larvae on pasture. American Journal of Veterinary Research 44: 395398.Google Scholar
Smith, G (1988). The population biology of the parasitic phase of Haemonchus contortus. Parasitology 96: 105195.CrossRefGoogle ScholarPubMed
Smith, G and Grenfell, BT (1994). Modelling of parasites populations: gastrointestinal nematode models. Veterinary Parasitology 54: 127143.Google Scholar
Soulsby, EJL (1965). Textbook of Veterinary Clinical Parasitology. Vol. 1. Helminths. Oxford: Blackwell, pp. 1120.Google Scholar
Sumbria, D and Sanyal, PK (2009). Exploiting nutrition-parasite interaction for sustainable control of gastrointestinal nematodosis in sheep. Vet Scan Vol 4, article 39. [Available from http://www.vetscan.co.in/v4n2/exploiting_nutrition_parasite_interaction_for_sustainable_control_of_gastrointestinal_nematodosis_in_sheep.htm Last accessed September 14, 2012].Google Scholar
Tembely, S, Lahlou-kassi, A, Rege, JEO, Sovani, S, Diedhiou, ML and Baker, RL (1997). The epidemiology of nematode infections in sheep in a cool tropical environment. Veterinary Parasitology 70: 129141.CrossRefGoogle Scholar
Thamsborg, SM (2001). Parasite control on organic sheep farms – options and limitations. In: Hovi, M andVaarst, M (eds) Positive health – preventive measures and alternative strategies. Proceedings NAHWOA Workshop. Vol. 5. Denmark: Rodding, pp. 92101.Google Scholar
Thamsborg, SM, Jörgensen, SM, Waller, PJ and Nansen, P (1996). The influence of stocking rate on gastrointestinal nematode infections of sheep over a two-year grazing period. Veterinary Parasitology 67: 207224.Google Scholar
Thamsborg, SM, Roepstorff, A and Larsen, M (1999). Integrated and biological control of parasites in organic and conventional production systems. Veterinary Parasitology 84: 169186.CrossRefGoogle ScholarPubMed
Thamsborg, SM, Larsen, M and Busch, M (2004). Sustainable, non-chemical control of small ruminant nematode parasites in Europe. In: Proceedings from an International Workshop held at Danish Centre of Experimental Parasitology, Royal Veterinary and Agricultural University, Denmark: Frederiksberg, 20–21 October 2004.Google Scholar
Thomas, RJ (1974). The effects of meteorological factors upon parasites. In: Symposium of the British Society for Parasitology, Taylor, AER and Muller, R (eds) 12: 1332.Google Scholar
Thornton, PK, van de Steeg, J, Notenbaert, A and Herrero, M (2009). The impacts of climate change on livestock and livestock systems in developing countries: a review of what we know and what we need to know. Agricultural Systems 101: 113127.CrossRefGoogle Scholar
Urquhart, GM, Armour, J, Duncan, JL, Dunn, AM and Jennings, FW (2002). Veterinary Parasitology, 2nd edn, Blackwell, pp. 323.Google Scholar
Valderrábano, J, Delfa, R and Uriarte, J (2002). Effect of level of feed intake on the development of gastrointestinal parasitism in growing lambs. Veterinary Parasitology 104: 327338.CrossRefGoogle ScholarPubMed
van Dijk, J and Morgan, ER (2011). The influence of water on the migration of infective Trichostrongyloid larvae onto grass. Parasitology 138: 19.Google Scholar
van Dijk, J, David, GP, Baird, G and Morgan, ER (2008). Back to the future: Developing hypotheses on the effects of climate change on ovine parasitic gastroenteritis from historical data. Veterinary Parasitology 158: 7384.CrossRefGoogle Scholar
van Dijk, J, Sargison, ND, Kenyon, F and Skuce, PJ (2010). Climate change and infectious disease: helminthological challenges to farmed ruminants in temperate regions. Animal 4: 377392.CrossRefGoogle ScholarPubMed
van Wyk, JA and Bath, GF (2002). The FAMACHA© system for managing haemonchosis in sheep and goats by clinically identifying individual animals for treatment. Veterinary Research 33: 509529.CrossRefGoogle ScholarPubMed
Van Wyk, JA and Reynecke, DP (2011). Blueprint for an automated specific decision support system for countering anthelmintic resistance in Haemonchus spp. at farm level. Veterinary Parasitology 177: 212223.CrossRefGoogle ScholarPubMed
Vynnycky, E and White, RG (2010). An Introduction to Infectious Disease Modelling. Oxford: Oxford University Press.Google Scholar
Wall, R and Ellse, LS (2011). Climate change and livestock parasites: integrated management of sheep blowfly strike in a warmer environment. Global Change Biology 17: 17701777.CrossRefGoogle Scholar
Waller, PJ (1997). Anthelmintic resistance. Veterinary Parasitology 72: 391412.CrossRefGoogle ScholarPubMed
Waller, PJ (1999). International approaches to the concept of integrated control of nematode parasites of livestock. International Journal of Parasitology 29: 155164.CrossRefGoogle Scholar
Waller, PJ and Thomas, RJ (1975). Field studies on inhibition of Haemonchus contortus in sheep. Parasitology 71: 285291.CrossRefGoogle Scholar
Waller, PJ and Thamsborg, SM (2004). Nematode control in ‘green’ ruminant production systems. Trends in Parasitology 20: 10.CrossRefGoogle ScholarPubMed
Waller, PJ, Dash, KM, Barger, IA, Le Jambre, LF and Plant, J (1995). Anthelmintic resistance in nematode parasites of sheep: learning from the Australian experience. Veterinary Record 136: 411413.CrossRefGoogle ScholarPubMed
Waller, PJ, Faedo, M and Ellis, K (2001). The potential of nematophagus fungi to control the free-living stages of nematode parasites of sheep: towards the development of a fungal controlled release device. Veterinary Parasitology 102: 299308CrossRefGoogle Scholar
Waller, PJ, Rudby-Martin, L, Ljungstrom, BL and Rydzik, A (2004a). The epidemiology of abomasal nematodes of sheep in Sweden, with particular reference to over-winter survival strategies. Veterinary Parasitology 122: 207220.Google Scholar
Waller, PJ, Schwan, O, Ljungström, B-L, Rydzik, A and Yeates, GW (2004b). Evaluation of biological control of sheep parasites using Duddingtonia flagrans under commercial arming conditions on the island of Gotland, Sweden. Veterinary Parasitology 126: 299315.CrossRefGoogle Scholar
Wells, A (1999). Integrated parasite management for livestock [online]. [Available from http://www.slideshare.net/ElisaMendelsohn/integrated-parasite-management-for-livestock Last accessed September 14, 2012].Google Scholar
White, F (1983). The vegetation of Africa, a descriptive memoir to accompany the UNESCO/AETFAT/UNSO Vegetation Map of Africa (3 Plates, Northwestern Africa, Northeastern Africa, and Southern Africa, 1:5,000,000). UNESCO, Paris.Google Scholar
Were, JLR (1998). Central Africa: Nigeria. A conservation assessment of terrestrial ecoregions of Africa: Draft proceedings of a workshop, Cape Town, South Africa, August 1998. Washington, DC, USA: World Wildlife Fund. [Available from http://worldwildlife.org/ecoregions/at1010 Last accessed September 19, 2012].Google Scholar
Young, RR, Anderson, N, Overend, D, Tweedie, RL, Malafant, KWJ and Preston, GAN (1980). The effect of temperature on times to hatching of eggs of the nematode Ostertagia circumcincta. Parasitology 81: 477491.CrossRefGoogle ScholarPubMed
Younie, D, Thamsborg, SM, Ambrosini, F and Roderick, S (2004). Grassland management and parasite control. In: Vaarst, M (ed.) Animal Health and Welfare in Organic Agriculture. Wallingford: CABI, pp. 309324.CrossRefGoogle ScholarPubMed