Outbreak Of Acute Disease Research Articles

Use of medicinal plants to control Haemonchus contortus infection in small ruminants

Haemonchus contortus is singly the most important of all the gastrointestinal nematodes that constrain the survival and productivity of sheep and goats owned by rural poor farmers in the developing world. This haematophagus parasite is infamous throughout the humid tropics/subtropics, being responsible for acute disease outbreaks with high levels of mortalities, particularly in young animals. Costs associated with control of this parasite in India, have been estimated to be US$ 103 million. H. contortus is also prominent amongst the reports of anthelmintic resistance that has emerged in all countries of the world that produce small ruminants. This emergence of multiple anthelmintic resistances has provided a spur for research on alternative forms of control. Recent surveys in developing countries have identified many plants that are intended and have the potential to be used as anthelmintics. This paper reviews the use of some medicinal plants as anthelmintics against H. contortus infection in small ruminants.

Infection by Trypanosoma vivax in goats and sheep in the Brazilian semiarid region: From acute disease outbreak to chronic cryptic infection

A study was undertaken to investigate the role of Trypanosoma vivax in sheep and goat mortality and abortions in the Brazilian semiarid region, where outbreaks had been previously reported in bovines. For this purpose, 177 goats and 248 sheep (20% of herds) were randomly sampled on four farms in the State of Paraiba in May and October 2008. The animals were screened for trypanosomes by the buffy coat technique (BCT) and PCR. Infected animals, ∼25% in both surveys, manifested apathy, pale mucous membranes, enlarged lymph nodes, weakness, weight loss, opacity of the cornea, blindness and abortion. However, the animals with acute and severe disease showing the highest levels of parasitemia and fever, which many times resulted in death, were only detected in the first survey. These severely diseased animals exhibited progressive weight loss and had the smallest packed cell volume (PCV) values. During survey 2, done in October 2008 on the same farms, only animals with low parasitemia and normal temperatures, PCV values and body weights were detected. Therefore, animals that spontaneously recovered from acute infection developed chronic and asymptomatic disease. This finding demonstrated for the first time that sheep and goats, which are the most important livestock in the semiarid region of Brazil, may be severely injured by T. vivax infection and also play a role as asymptomatic carriers and important sources of T. vivax to ruminants in general.

Acute viral and bacterial infections elevate water cortisol concentrations in fish tanks

Freshwater rainbow trout and Atlantic salmon were experimentally challenged with Viral Haemorrhagic Septicaemia virus and Aeromonas salmonicida respectively, and daily measurements made of cortisol release into the water for 5–7 days post-challenge. There was a surge in cortisol release into the water one to two days before mortality became apparent in both challenges. These experiments and a review of other literature demonstrate that cortisol elevation is a common feature of fish experiencing acute infections. The cortisol response of fish to pathogen infections, and the possible use of water cortisol surges for early warning of acute disease outbreaks on fish farms, are discussed.

WHO's Response to Global Public Health Threats: XDR-TB

(This letter appears in response to the May 2007 PLoS Medicine Editorial: “How Is WHO Responding to Global Public Health Threats?” [1]) The travels of a patient with extensively drug-resistant tuberculosis (XDR-TB) from North America to Europe and back have heightened concerns about this growing global disease problem and the possibility of its international transmission through travel. The seriousness of this possibility raises the question of whether XDR-TB cases or outbreaks may constitute public health emergencies of international concern (PHEICs) under the 2005 International Health Regulations (IHR 2005), which became binding international law on June 15, 2007 [2]. XDR-TB may be the first case of a public health problem that tests how States Parties and the World Health Organization (WHO) apply the IHR 2005. We believe that cases or outbreaks of XDR-TB would meet the notification criteria of the IHR 2005 as events that may constitute a PHEIC because they trigger affirmative answers to at least two of the four questions in the IHR 2005's decision instrument (Annex 2, [3]). Thus, as of June 15, 2007, States Parties must report such cases or outbreaks to WHO pursuant to the IHR 2005. XDR-TB triggers an affirmative answer to the decision instrument's question: “Is the public health impact of the event serious?”, both because of the possibility of the event having a high public health impact and, in many instances, the need for external assistance in managing cases. XDR-TB cases would likely produce an affirmative answer to the question: “Is the event unusual or unexpected?”, because of the higher than expected case-fatality rates, particularly where XDR-TB occurs with high prevalence of HIV infection. The disease also may generate a positive answer to the question: “Is there a significant risk of international travel or trade restrictions?”, primarily because of the possibility of international media attention. At present, XDR-TB would arguably not produce a clearly affirmative answer to the question: “Is there a significant risk of international spread?”, because epidemiological data linking XDR-TB outbreaks and cases with the international movement of people are weak. Experience with TB, multi-drug-resistant TB (MDR-TB), and XDR-TB demonstrates, however, that cross-border spread is a very real threat. XDR-TB has already spread from one province to several provinces in South Africa, and has in all likelihood crossed African borders, but confirmation is delayed because of inadequate surveillance capabilities. It remains less certain whether the WHO Director-General would determine that XDR-TB cases or outbreaks notified to WHO would constitute a PHEIC. This would lead to the issuance of temporary recommendations to States Parties, which could include travel restrictions and use of compulsory measures such as quarantine or isolation. In February 2007, the WHO Global Task Force on XDR-TB argued against such a position because “the new regulations are aimed particularly to situations where there is a significant risk of international spread” and that temporary recommendations “are really intended for outbreaks of acute disease, rather than the ‘acute-on-chronic’ situation of MDR-TB and XDR-TB” [4]. The Global Task Force stated that, if international spread of XDR-TB were demonstrated, then standing recommendations should be considered. To some extent, the recommendations and alerts WHO has already issued on XDR-TB suggest that treating XDR-TB as a routine public health risk is not adequate. In addition, the IHR 2005 does not limit its scope of application to “acute disease” [5]. TB has never been an acute risk in the same manner as a pandemic strain of influenza, but history attests to TB's persistence as a lethal global threat, especially for vulnerable populations. As the global XDR-TB problem becomes more severe, more robust and drastic public health actions may be required nationally and globally, including a declaration from the WHO Director-General of the existence of a PHEIC. A window of opportunity may exist now for effective international action to control the spread of the disease, and the IHR 2005 may provide a mechanism to help achieve this objective. A narrow, limited reading of the IHR 2005's scope of application could undermine its ability to contribute to this global health crisis.

Nutrition and lameness in dairy cattle - a different perspective?

Lameness due to foot problems in dairy cattle can be divided into two categories. The first of these categories is infectious lameness, which is primarily caused by digital dermatitis and foul-in-the foot. The second category is made up of the non-infectious diseases which affect the claw horn. In the UK these are primarily sole ulcer and white-line disease, with around 40% of reports of lameness by NADIS vets being associated with these diseases. While there may be some link between diet and infectious hoof horn disease (e.g. wetter diets - more slurry - more digital dermatitis), it is the claw horn diseases which are most often linked to nutrition; indeed they are often said to be caused by laminitis, a term which implies a nutritional aetiology. However, much recent research has questioned the laminitic aetiology of cla w horn disease and thus the importance of nutrition as the primary cause of white line disease and sole ulcers. LAMINITIS AND LAMENESS IN DAIRY CATTLE Acute laminitis as a result of inappropriate feeding, particularly starchy concentrates is a well recognised cause of acute lameness in cattle. However in dairy cattle such acute outbreaks of disease are sporadic and cannot be responsible for the large numbers of co ws which are lame due to white line disease or sole ulcer. Instead it has been hypothesised that claw horn diseases are due to ‘subclinical laminitis’, resulting from a subacute ruminal acidosis. The hypothesis is that this subacute acidosis leads to the release of vasoactive substances (particularly histamine and/or endotoxins) which cause vasoconstriction and dilation in the hoof blood v essels destroying the microvasculature of the corium. This produces ischaemia which results in haemorrhage and hoof horn damage, and ultimately claw horn disease. However this hypothesis is still unproven. Giving cows endotoxins or histamine does not produce claw horn disease; there is no evidence that hoof haemorrhages are associated with an acute phase

Containing Acute Disease Outbreak

The objectives of epidemiological surveillance and research of infectious diseases are to address disease prevention, identify outbreaks and monitor and evaluate control strategies. In this paper, we report on the development of a Geographical Information System (GIS) based on a novel Digital Ring Fence (DRiF) strategy for the containment of acute infectious diseases. Data from probable cases are captured in a secure database. Postal codes of addresses facilitate precise mapping of the location of each probable case on a multi-layered GIS system. A digital ring fence is constructed around each location (hot-spot) using Non- Homogeneous Poisson Process (NHPP) modeling based on data of individuals coming into contact with each probable case. The radius of the DRiF gives the overall risk of infection from its epicenter, the probable case. By annotating the DRiF to a GIS, areas of population concentrations could be readily identified to direct outbreak containment efforts. Simulation studies have demonstrated that the DRiF strategy could provide a novel approach to containment of acute disease outbreaks. SARS has provided convincing evidence that the key to tackling acute infectious disease outbreaks lies in containment and making disease containment one step ahead of its spread. The DriF strategy achieves this by providing a zone to corral the spread of infection through person-to-person transmission. Other useful applications of the DriF technique include demarcating culling zone for the containment of bird flu infection and containment of person-to-person transmission should it occur.

The necrotizing enteritis by Clostridium perfringens type C in piglets: practical observations, control and epidemiology

Necrotizing enteritis in piglets is caused by the spore-forming anaerobe Clostridium perfringens type C. The pathology is believed to be due to the production of beta-toxin by the agent and the infection tends to persist in affected herds despite appropriate hygiene measures. During the period 1989 to 2001, 35 outbreaks were observed in 15 herds in a limited geographic region in northwestern Switzerland in the canton of Fribourg. Initial outbreaks of acute disease were followed by chronic manifestations of necrotizing enteritis in eleven herds. Since clinical symptoms in case of chronic necrotizing enteritis and of mixed infections were rather non-specific, diagnosis in all herds was confirmed by gross pathological analysis, intestinal histology and bacteriological culture. After initial evaluation in 135 litters (1500 piglets), metaphylaxis consisted of penicillin for outbreaks of acute disease or of amoxycillin-clavulanic acid pending results of laboratory confirmation. Vaccination with a C. perfringens toxoid vaccine (Gletvax 6, also containing E. coli pilus antigens) together with penicillin chemoprophylaxis was used in 2400 litters (27,000 piglets). In 12 to 17% of litters disease recurred during this combined prophylaxis. Necrotizing enteritis persisted in all affected herds throughout the follow-up period.

Immunohistochemical detection of VHS virus in paraffin-embedded specimens of rainbow trout (Oncorhynchus mykiss): the influence of primary antibody, fixative, and antigen unmasking on method sensitivity.

The influence of the primary antibody, the fixative, and the antigen unmasking technique on the method sensitivity of immunohistochemistry as a method for the identification of viral hemorrhagic septicemia (VHS) virus in paraffin-embedded specimens of naturally infected rainbow trout (Oncorhynchus mykiss) was examined. Fish (200-300 g) were collected during an outbreak of VHS. Parallel specimens from liver, spleen, kidney, and brain were fixed by immersion in 10% phosphate-buffered formalin, periodate-lysine-paraformaldehyde (PLP), Bouin's fluid, or absolute ethanol. Virus cultivation was also performed on parallel specimens, and the virus titer (TCID50/ml) was determined. Purified nucleocapsid protein (N-protein) of the virus was incorporated in an artificial antigen substrate polymerized bovine serum albumin), fixed as described above, and embedded in paraffin wax. Microwave unmasking was performed on formalin-, PLP-, and Bouin's fluid-fixed specimens. The presence of virus peptides in situ or N-protein in the artificial antigen substrates was visualized using an immunohistochemical method based on alkaline phosphatase or peroxidase and one polyclonal and five monoclonal polypeptide-specific antibodies. VHS virus was identified in situ in specimens with high virus titers (10(7-8) TCID50/ml) regardless of the fixative and without the need of an unmasking procedure. A pronounced masking effect was observed for the cross-linking formalin and PLP fixatives. Regardless of the primary antibodies used, there was a significantly higher epidemiologic sensitivity (the proportion of virus positive samples that tested positive by immunohistochemistry) using ethanol and Bouin's fluid compared with formalin and PLP (P < 0.05). At 10(5) TCID50/ml, the average sensitivity reached 0.5, and at > or = 10(6) TCID50/ml, sensitivity was 0.9. Unmasking procedures showed a moderate effect and did not result in significantly higher epidemiologic sensitivity (P = 0.17), There was great variation for the different monoclonal antibodies/antigens and fixatives. Sensitivity studies on antigen substrates were in accordance with results of in situ studies that showed the highest sensitivity for ethanol and Bouin's fluid. Virus cultivation was more sensitive than immunohistochemistry. This study showed that the fixative and the primary antibody both influence method sensitivity and that VHS virus antigens concealed during fixation are difficult to reexpose. Immunostaining for VHS virus should be performed with monoclonal antibodies specific for the N-protein, and tissue samples should be fixed in either ethanol or Bouin's fluid. Immunohistochemistry is specific but is less sensitive than virus cultivation. Immunostaining for VHS virus can be a valuable supplement to virus cultivation during acute outbreaks of disease.

Occurrence and Distribution ofAeromonas salmonicidaInfections on Swedish Fish Farms, 1951–1987

The occurrence of typical and atypical Aeromonas salmonicida infections on Swedish fish farms was surveyed, and the methods for controlling the disease are described here. This review is based on data for a period of 36 years from fish health control studies conducted by the National Veterinary Institute and the Salmon Research Institute. The epizootiology and routes of transmission of the pathogens are described, and policy and methods for disease control are discussed. The distribution of atypical A. salmonicida infections was entirely different from that of typical infections. There was also circumstantial evidence of different routes of transmission for typical and atypical A. salmonicida infections. Although subclinical carriers of atypical A. salmonicida occurred among Atlantic salmon Salmo salar and rainbow trout Oncorhynchus mykiss on fish farms, acute disease outbreaks were most frequent among Arctic char Salvelinus alpinus and brown trout Salmo trutta. On the other hand, acute outbreaks of typical A. salmonicida infections were frequent among Atlantic salmon and rainbow trout.

Natural and experimentally induced lesions of the body wall of the sea urchin Strongy-locentrotus droebachiensis

Lesions of the body wall occurred in about 7 % of sea urchins Strongylocentrotus droebachiensis in a healthy population off Nova Scotia, Canada. Lesions occurred predominantly in the oral hemisphere in both ambulacral and interambulacral areas. On average, lesions covered 8 to 12 % of the total test surface of individuals, although lesion size was quite variable. Lesioned areas of test generally were darkly pigmented, covered with a mucoid layer, and devoid of spines, pedicellariae and tube feet. Three morphological types of lesions were identified, which appeared as progressive stages: Stage 1 w ~ t h a thln mucoid layer, nearly transparent to pinlush in coloration; Stage 2 with a thick more darkly p~gmented mucoid layer, ranging from reddish to purplish-black; and Stage 3 with spine regeneration through a pigmented mucoid layer. The test in lesioned areas was often friable, but rarely perforated. Scannlng electron microscopy ind~cated extensive degeneration of the epidermis and stereom. Gonads of lesioned Individuals were frequently discoloured, but gonad slzes were not significantly different between healthy and lesioned ~ndividuals. Microflora normally found on healthy body surfaces of the sea urchin proliferated in lesioned areas. Of 85 isolates identified from swab samples of lesioned and healthy test surfaces, 93 8 0 were Gram-negative bacteria belonging mainly to the taxa Acinetobacter, Alcaligenes, Flavobacterium, Pseudomonas and Enterobacteriaceae. The total number of microorganisms and the numbers of Acinetobacter and Alcaligenes were significantly higher on lesioned surfaces (Stage 1 or Stage 2) than on healthy surfaces of the same individuals. Most bacterial types increased in abundance from Stage 1 to Stage 2 lesions, although this increase was statistically significantly only for Acinetobacter. Vibrionaceae, Cram-positive bacteria and fungi occurred sporadically and in low abundance on lesioned and healthy test surfaces. Mechanical abrasion of the test surface of the sea urchin produced lesions s~rnilar in gross morphology to naturally occurring ones. In laboratory experiments, lesions developed in all abraded individuals, Irrespective of exposure to iesioned or healthy conspecifics either by a waterborne route or by direct contact. Lesion development was accelerated, and recovery retarded, by directly contacting the abraded test surface with material from a natural lesion. Unabraded sea urchins did not develop lesions ~ n d i c a t ~ n g that removal of the epidermis provides a route of infection. Rate of recovery of experimentally abraded individuals (as measured by spine regeneration and reduction in lesion size) was significantly higher at 16OC than at 3°C. Provision of food (kelp) had a significant positive effect on recovery after 12 wk. Body wall lesions of S. droebachiensis appear to be symptoms of chronic, superficial infections from which sea urchins generally recover. The increased incidence of lesions in this species (and others) during or after outbreaks of acute disease may reflect secondary bacterial and/or fungal infections.

Fascioliasis in New Zealand: A review

Intermediate hosts of Fasciola hepatica in New Zealand are the native species Lymnaea tomentosa, and introduced species, L. columella and L. truncatula. The latter is of little significance in New Zealand. Fascioliasis has become more widespread since 1950 following colonisation of much of the North Island by L. columella. L. tomentosa can produce eggs at 5°C and L. columella at 2°C. L. columella produces about the three times as many eggs as L. tomentosa and the eggs of the former develop more rapidly and over a wider range of temperatures. Both species inhabit ponds and marshes, although L. columella is better suited to pond habitats. Neither species will survive in marsh habitats that dry out in summer. Both species tolerate wide ranges of Ca and Mg concentrations and pH. Marsh habitats of the two species are indistinguishable though there is evidence of subtle differences in habitat preferences. Snail populations are minimal in winter and fluctuate irregularly throughout the rest of the year. In general, L. tomentosa populations contain proportionally more mature snails than those of L. columella. The epidemiology of fascioliasis in New Zealand is discussed. The absence of outbreaks of acute disease, the multiplicity of snail hosts and variations in climate pose problems for investigators. Overwintering infections of snails have been observed in L. tomentosa, but not in L. columella. With the latter host, transmission of Fasciola occurred over 6–7 months from mid-summer to mid-winter. The rate of infection of tracer sheep over 5 years varied but was not related to temperature or increased summer rainfall. Infection rates tended to increase when summers were dry and animals forced to graze the snails habitats. Rates in infection were not related to snail densities but to the numbers of mature snails on habitats. The infection rate of L. columella was extremely low ( 1 790 snails examined). Sheep appear to be more important than cattle in maintaining Fasciolainfections from year to year. The control of fascioliasis is discussed briefly. It is argued that prevention of infection is preferable to removing infections already acquired, and low this might be achieved by a strategic anthelmintic treatment when L. columella is involved is described. Further studies on the prevalence and epidemiology of fascioliasis in New Zealand are required.

Trichostrongyle worm infection in cattle: Ostertagiasis—Effect of a field outbreak on production, with a review of the disease syndromes, problems of diagnosis and treatment

Abstract Extract The problem of parasitism in cattle in New Zealand has been largely neglected, except in acute disease outbreaks. Losses, apparently due to chronic or subclinical parasitic gastro-enteritis, have been either undiagnosed or ignored, or the measures required to prevent these losses have been considered uneconomic or impractical. This latter view can perhaps be attributed to the low efficacy of anthelmintics previously available. Now, at a time when greatly improved standards of prophylaxis and treatment are offered by the new broad-spectrum anthelmintics, new difficulties in control have become apparent.

The significance ofNematodirusin New Zealand

Abstract Extract Although Nematodirus species are commonlyfound in sheep in New Zealand, the worm had been considered to be of little economic importance until the period 1956–9 when a number of outbreaks of acute disease occurred in lambs; the condition was ascribed to heavy Nematodirus infestation. A similar situation had existed in the British Isles until about 1951 when outbreaks of acute nematodiriasis reached serious proportions.