Seasonal influences on livestock keeping in a sedentary crop-livestock system.

Although seasonality is recognised as an important part of agricultural-based livelihoods, limited literature is available on the subject area, and it is often only alluded to in discussion of other aspects of rural livelihoods. A 2-year longitudinal study to examine the influences of seasonal changes on livestock keeping in a smallholder crop-livestock production system was carried out in Busia District, western Kenya. The study aimed to obtain a picture of yearly variations in household activities and resources, as a means of understanding decisions made by households regarding animal health management, and household times of vulnerability in terms of losing animals. Data collection coincided with the three main seasons in the study area. Information on (inter alia) seasonal livelihood activities, animal health care expenses, numbers of disease episodes and livestock movements into and out of households was collected using questionnaires and participatory rural appraisal methodologies. Farmers suggested clear and consistent seasonal changes and events, but data analyses did not show the patterns expected in relation to livestock keeping. Important observations were made in relation to livestock disease episodes and the use of veterinary services; livestock disease episodes were higher during the long rains than in the dry season, but more money was spent during the dry season when numbers of disease episodes were low, and more households also used professional veterinary services during this season (chi(2) = 81.47, P < 0.001). In both study years, a higher proportion of households treated animals themselves during the rainy seasons (z = -2.4, P = 0.02; z = -5.03, P < 0.001).

Farmer estimation of live bodyweight of cattle: implications for veterinary drug dosing in East Africa.

The ability of smallholder farmers and animal health workers to estimate live bodyweight can critically affect the likelihood of under- or over-dosing of veterinary compounds in decentralised systems where farmers administer a significant proportion of the veterinary treatments. A survey of 324 cattle owned by 170 farmers was conducted in Busia District, Kenya. Cattle were weighed on a standard calibrated scale and owners were asked to estimate the live weight of their animals. Weights were also estimated by a weigh-band and by local animal health workers. Cattle owners consistently underestimated the weights of their cattle; 85.7% of the cattle had their bodyweights underestimated by an average of 46.9% of their true weight. Furthermore, very few cattle (19.0%) had their weights estimated accurately to within +/-20% of their true weight by these farmers, an accuracy range important for drug dosing. This finding raises concerns of widespread under-dosing of cattle with trypanocidal and other veterinary drugs. Animal health workers were better at estimating live bodyweight of cattle; 76.6% of cattle were estimated accurately to within +/-20% of their true weight. It is possible to improve farmers' and animal health workers' ability to estimate accurately live bodyweight of cattle with appropriate training. Evidence of this was provided by animal health workers whose estimates improved over time as they received feedback of the true weights of different sizes of cattle from the standard scale.

Tsetse fly evolution, genetics and the trypanosomiases - A review.

This reviews work published since 2007. Relative efforts devoted to the agents of African trypanosomiasis and their tsetse fly vectors are given by the numbers of PubMed accessions. In the last 10 years PubMed citations number 3457 for Trypanosoma brucei and 769 for Glossina. The development of simple sequence repeats and single nucleotide polymorphisms afford much higher resolution of Glossina and Trypanosoma population structures than heretofore. Even greater resolution is offered by partial and whole genome sequencing. Reproduction in T. brucei sensu lato is principally clonal although genetic recombination in tsetse salivary glands has been demonstrated in T. b. brucei and T. b. rhodesiense but not in T. b. gambiense. In the past decade most genetic attention was given to the chief human African trypanosomiasis vectors in subgenus Nemorhina e.g., Glossina f. fuscipes, G. p. palpalis, and G. p. gambiense. The chief interest in Nemorhina population genetics seemed to be finding vector populations sufficiently isolated to enable efficient and long-lasting suppression. To this end estimates were made of gene flow, derived from FST and its analogues, and Ne, the size of a hypothetical population equivalent to that under study. Genetic drift was greater, gene flow and Ne typically lesser in savannah inhabiting tsetse (subgenus Glossina) than in riverine forms (Nemorhina). Population stabilities were examined by sequential sampling and genotypic analysis of nuclear and mitochondrial genomes in both groups and found to be stable. Gene frequencies estimated in sequential samplings differed by drift and allowed estimates of effective population numbers that were greater for Nemorhina spp than Glossina spp. Prospects are examined of genetic methods of vector control. The tsetse long generation time (c. 50 d) is a major contraindication to any suggested genetic method of tsetse population manipulation. Ecological and modelling research convincingly show that conventional methods of targeted insecticide applications and traps/targets can achieve cost-effective reduction in tsetse densities.

Crisis, what crisis? Control of Rhodesian sleeping sickness.

There is an urgent need for cost-effective strategies for the sustainable control of Trypanosoma brucei rhodesiense (Rhodesian) sleeping sickness, which is a fatal zoonotic disease that has caused devastating epidemics during the past century. Sleeping sickness continues to be controlled by crisis management, using active case detection, treatment and vector control - activities that occur only during major epidemics; during the intervening periods, farmers and communities must fend for themselves. There are several methods for assessing the burden of this disease and there is a series of farmer-led methodologies that can be applied to reduce the burden of human and animal trypanosomiases.

Beyond Tsetse--Implications for Research and Control of Human African Trypanosomiasis Epidemics.

Epidemics of both forms of human African trypanosomiasis (HAT) are confined to spatially stable foci in Sub-Saharan Africa while tsetse distribution is widespread. Infection rates of Trypanosoma brucei gambiense in tsetse are extremely low and cannot account for the catastrophic epidemics of Gambian HAT (gHAT) seen over the past century. Here we examine the origins of gHAT epidemics and evidence implicating human genetics in HAT epidemiology. We discuss the role of stress causing breakdown of heritable tolerance in silent disease carriers generating gHAT outbreaks and see how peculiarities in the epidemiologies of gHAT and Rhodesian HAT (rHAT) impact on strategies for disease control.

Cattle owners' perceptions of African bovine trypanosomiasis and its control in Busia and Kwale Districts of Kenya.

A study using a structured questionnaire was conducted in Busia District, Western Kenya and Kwale District, Coastal Kenya to obtain qualitative and quantitative information from 256 cattle owners about their production systems, their perceptions of the diseases encountered in their cattle, the drugs used, and other measures adopted to control trypanosomiasis in cattle. The predominant production system was mixed crop-livestock with farmers owning 2-11 local cattle on holdings between 2 and 5 ha. Approximately 15% of disease episodes in cattle were perceived to be trypanosomiasis, although the farmers' ability to make diagnoses was limited in that over half of the diagnoses were inconsistent with the clinical signs described. Drugs were generally obtained from agro-veterinary shops, and the farmers themselves administered slightly more than half of these. One third of drug treatments given to sick cattle were trypanocides, but over half of these trypanocidal treatments were given to cattle believed to have diseases other than trypanosomiasis.

Priorities for the elimination of sleeping sickness.

Sleeping sickness describes two diseases, both fatal if left untreated: (i) Gambian sleeping sickness caused by Trypanosoma brucei gambiense, a chronic disease with average infection lasting around 3 years, and (ii) Rhodesian sleeping sickness caused by T. b. rhodesiense, an acute disease with death occurring within weeks of infection. Control of Gambian sleeping sickness is based on case detection and treatment involving serological screening, followed by diagnostic confirmation and staging. In stage I, patients can remain asymptomatic as trypanosomes multiply in tissues and body fluids; in stage II, trypanosomes cross the blood-brain barrier, enter the central nervous system and, if left untreated, death follows. Staging is crucial as it defines the treatment that is prescribed; for both forms of disease, stage II involves the use of the highly toxic drug melarsoprol or, in the case of Gambian sleeping sickness, the use of complex and very expensive drug regimes. Case detection of T. b. gambiense sleeping sickness is known to be inefficient but could be improved by the identification of parasites using molecular tools that are, as yet, rarely used in the field. Diagnostics are not such a problem in relation to T. b. rhodesiense sleeping sickness, but the high level of under-reporting of this disease suggests that current strategies, reliant on self-reporting, are inefficient. Sleeping sickness is one of the 'neglected tropical diseases' that attracts little attention from donors or policymakers. Proper quantification of the burden of sleeping sickness matters, as the primary reason for its 'neglect' is that the true impact of the disease is unknown, largely as a result of under-reporting. Certainly, elimination will not be achieved without vast improvements in field diagnostics for both forms of sleeping sickness especially if there is a hidden reservoir of 'chronic carriers'. Mass screening would be a desirable aim for Gambian sleeping sickness and could be handled on a national scale in the endemic countries - perhaps by piggybacking on programmes committed to other diseases. As well as improved diagnostics, the search for non-toxic drugs for stage II treatment should remain a research priority. There is good evidence that thorough active case finding is sufficient to control T. b. gambiense sleeping sickness, as there is no significant animal reservoir. Trypanosoma brucei rhodesiense sleeping sickness is a zoonosis and control involves interrupting the fly-animal-human cycle, so some form of tsetse control and chemotherapy of the animal reservoir must be involved. The restricted application of insecticide to cattle is the most promising, affordable and sustainable technique to have emerged for tsetse control. Animal health providers can aid disease control by treating cattle and, when allied with innovative methods of funding (e.g. public-private partnerships) not reliant on the public purse, this approach may prove more sustainable. Sleeping sickness incidence for the 36 endemic countries has shown a steady decline in recent years and we should take advantage of the apparent lull in incidence and aim for elimination. This is feasible in some sleeping sickness foci but must be planned and paid for increasingly by the endemic countries themselves. The control and elimination of T. b. gambiense sleeping sickness may be seen as a public good, as appropriate strategies depend on local health services for surveillance and treatment, but public-private funding mechanisms should not be excluded. It is timely to take up the tools available and invest in new tools - including novel financial instruments - to eliminate this disease from Africa.

Neglected and endemic zoonoses.

Endemic zoonoses are found throughout the developing world, wherever people live in close proximity to their animals, affecting not only the health of poor people but often also their livelihoods through the health of their livestock. Unlike newly emerging zoonoses that attract the attention of the developed world, these endemic zoonoses are by comparison neglected. This is, in part, a consequence of under-reporting, resulting in underestimation of their global burden, which in turn artificially downgrades their importance in the eyes of administrators and funding agencies. The development of cheap and effective vaccines is no guarantee that these endemic diseases will be eliminated in the near future. However, simply increasing awareness about their causes and how they may be prevented-often with very simple technologies-could reduce the incidence of many endemic zoonoses. Sustainable control of zoonoses is reliant on surveillance, but, as with other public-sector animal health services, this is rarely implemented in the developing world, not least because of the lack of sufficiently cheap diagnostics. Public-private partnerships have already provided advocacy for human disease control and could be equally effective in addressing endemic zoonoses.

Effects of cyclic nucleotides on midgut infections and maturation of T. b. brucei in G. m. morsitans.

Cyclic nucleotide signalling through cyclic adenosine monophosphate (cAMP) is thought to play an important role in the transformation of the long slender (dividing) form to the short-stumpy (arrested) form in the mammalian bloodstream but the role of cyclic nucleotides in the tsetse-based part of the trypanosome life cycle is unknown. In a series of in vivo experiments, it was found that cyclic guanosine monophosphate (cGMP) but not cAMP could induce significantly higher rates of midgut infection in tsetse. Continuous feeding of either cGMP or cAMP to tsetse had no effect on rates of maturation of established midgut infections suggesting that these two parts of the life cycle in tsetse are not linked.

A novel procedure for total nucleic acid extraction from small numbers of Eimeria species oocysts.

A series of experiments were performed in an attempt to extract genomic DNA from a small number of Eimerian oocysts. Sonication, ammonia, ethanol and lysozyme were all found to be unsuitable for the digestion of Eimeria oocysts. The chemicals and enzyme given were not capable of either disruption or digestion of oocysts for nucleic acid extraction. They had the capability of penetrating the oocyst wall but could not break-up the oocyst wall. It is impossible to obtain nucleic acid from Eimeria oocysts if the wall is not broken-up. In this study oocyst disruption was achieved using a simple but highly effective treatment regime involving sodium hypochlorite treatment, osmotic shock and proteinase K digestion. Following the disruption of the oocyst walls, a commercially available nucleic acid purification kit (Wizard DNA Purification Kit, Promega) can be used to prepare high quality nucleic acid.

Factors affecting trypanosome maturation in tsetse flies.

Trypanosoma brucei brucei infections which establish successfully in the tsetse fly midgut may subsequently mature into mammalian infective trypanosomes in the salivary glands. This maturation is not automatic and the control of these events is complex. Utilising direct in vivo feeding experiments, we report maturation of T. b. brucei infections in tsetse is regulated by antioxidants as well as environmental stimuli. Dissection of the maturation process provides opportunities to develop transmission blocking vaccines for trypanosomiasis. The present work suggests L-cysteine and/or nitric oxide are necessary for the differentiation of trypanosome midgut infections in tsetse.

Theileria parva candidate vaccine antigens recognized by immune bovine cytotoxic T lymphocytes.

East Coast fever, caused by the tick-borne intracellular apicomplexan parasite Theileria parva, is a highly fatal lymphoproliferative disease of cattle. The pathogenic schizont-induced lymphocyte transformation is a unique cancer-like condition that is reversible with parasite removal. Schizont-infected cell-directed CD8(+) cytotoxic T lymphocytes (CTL) constitute the dominant protective bovine immune response after a single exposure to infection. However, the schizont antigens targeted by T. parva-specific CTL are undefined. Here we show the identification of five candidate vaccine antigens that are the targets of MHC class I-restricted CD8(+) CTL from immune cattle. CD8(+) T cell responses to these antigens were boosted in T. parva-immune cattle resolving a challenge infection and, when used to immunize naïve cattle, induced CTL responses that significantly correlated with survival from a lethal parasite challenge. These data provide a basis for developing a CTL-targeted anti-East Coast fever subunit vaccine. In addition, orthologs of these antigens may be vaccine targets for other apicomplexan parasites.

Sleeping sickness in Uganda: a thin line between two fatal diseases.

OBJECTIVE: To determine, through the use of molecular diagnostic tools, whether the two species of parasite that cause human African trypanosomiasis have become sympatric. DESIGN: Blood sampling of all available patients between June 2001 and June 2005 in central Uganda and between July and September 2003 in northwest Uganda and analysis of subcounty sleeping sickness records in Uganda between 1985 and 2005. SETTING: Sleeping sickness treatment centres in central and northwest Uganda and in south Sudan. PARTICIPANTS: Patients presenting at the treatment centres and diagnosed as having sleeping sickness. MAIN OUTCOME MEASURE: Classification of parasites from patients from each disease focus as either Trypanosoma brucei rhodesiense (acute form) or T b gambiense (chronic form). RESULTS: Blood from 231 patients with sleeping sickness in central Uganda and from 91 patients with sleeping sickness in northwest Uganda and south Sudan were screened for T b rhodesiense (detection of SRA gene) and T b gambiense (detection of TgsGP gene). All samples from central Uganda were classified as T b rhodesiense, and all samples from northwest Uganda and south Sudan were identified as T b gambiense. CONCLUSIONS: The two focuses of human African trypanosomiasis remain discrete, but the area of Uganda affected by the acute form of human sleeping sickness has increased 2.5-fold since 1985, spreading to three new districts within the past five years through movement of infected livestock. Without preventive action targeted at the livestock reservoir of this zoonotic disease, it is likely that the two disease focuses will converge. This will have a major impact on diagnosis and treatment of this neglected disease. Real time monitoring is recommended, using molecular diagnostic tools (at a regional surveillance centre, for example) targeted at both livestock and human patients.

Conservation of capa peptide-induced nitric oxide signalling in Diptera.

In D. melanogaster Malpighian (renal) tubules, the capa peptides stimulate production of nitric oxide (NO) and guanosine 3', 5'-cyclic monophosphate (cGMP), resulting in increased fluid transport. The roles of NO synthase (NOS), NO and cGMP in capa peptide signalling were tested in several other insect species of medical relevance within the Diptera (Aedes aegypti, Anopheles stephensi and Glossina morsitans) and in one orthopteran out-group, Schistocerca gregaria. NOS immunoreactivity was detectable by immunocytochemistry in tubules from all species studied. D. melanogaster, A. aegypti and A. stephensi express NOS in only principal cells, whereas G. morsitans and S. gregaria show more general NOS expression in the tubule. Measurement of associated NOS activity (NADPH diaphorase) shows that both D. melanogaster capa-1 and the two capa peptides encoded in the A. gambiae genome, QGLVPFPRVamide (AngCAPA-QGL) and GPTVGLFAFPRVamide (AngCAPA-GPT), all stimulate NOS activity in D. melanogaster, A. aegypti, A. stephensi and G. morsitans tubules but not in S. gregaria. Furthermore, capa-stimulated NOS activity in all the Diptera was inhibited by the NOS inhibitor l-NAME. All capa peptides stimulate an increase in cGMP content across the dipteran species, but not in the orthopteran S. gregaria. Similarly, all capa peptides tested stimulate fluid secretion in D. melanogaster, A. aegypti, A. stephensi and G. morsitans tubules but are either without effect or are inhibitory on S. gregaria. Consistent with these results, the Drosophila capa receptor was shown to be expressed in Drosophila tubules, and its closest Anopheles homologue was shown to be expressed in Anopheles tubules. Thus, we provide the first demonstration of physiological roles for two putative A. gambiae neuropeptides. We also demonstrate neuropeptide modulation of fluid secretion in tsetse tubule for the first time. Finally, we show the generality of capa peptide action, to stimulate NO/cGMP signalling and increase fluid transport, across the Diptera, but not in the more primitive Orthoptera.