PubMed Health⌕ Search

Biomedical subjects

C N Macpherson

Publications and source records attributed to C N Macpherson.

At least 19 recordsLinked to original sources
PubMed2000

Parasitic food-borne and water-borne zoonoses.

Estimates suggest that almost half of the population of the world is affected by water-borne and food-borne infections. Parasitic food-borne and water-borne zoonoses contribute to this statistic by inflicting a heavy toll on human health and causing serious direct and indirect losses to the agricultural industry. The inability of non-industrialised countries to keep pace with population growth, migration from rural to urban areas and the demand for clean, safe drinking water and proper sanitation means that water-borne zoonoses will continue to exact an increasing burden of ill health in these countries. The consumption of raw or undercooked meat, crustaceans, and fresh-water fish and vegetables facilitates transmission of large numbers of zoonotic infections. The burgeoning tourist industry, emigration and the importation of food from endemic regions has resulted in increasing diagnosis of these infections in non-endemic countries. The authors examine the epidemiology, medical and veterinary public health importance and recent developments in diagnosis, treatment and control of the most important parasitic food-borne and water-borne infections.

Animals↗
PubMed1999

An extensive ultrasound and serologic study to investigate the prevalence of human cystic echinococcosis in northern Libya.

A prevalence study of abdominal cystic echinococcosis (CE) was undertaken in the northwest, north-central, and northeast regions of Libya. A total of 36 villages along the coast were included, in which 20,220 people were screened by portable ultrasound. Three hundred thirty-nine (1.7%) were diagnosed with CE. There was no significant difference between CE prevalence rates in the three regions of Libya (mean = 1.6%); however, intervillage rates were variable, ranging from 0% to 4.5%. The prevalence of CE increased significantly with age (P < 0.0001) and females were significantly more affected (2%) than males (1.3%) (P < 0.0001). Cases of CE were distributed among 3.2% of housewives, 2.6% of farmers, 2.3% of male civil servants, 1.3% of female students, and 1.1% of male students. Housewives (P < 0.0001) and students (P < 0.0001) were significantly more at risk for CE. A statistically significant proportion (62% [210 of 339]) of CE cases kept dogs (P < 0.0001). Of the ultrasound-positive CE cases 69% (233 of 339) were antibody seropositive by ELISA using Echinococcus granulosus hydatid cyst fluid antigen B. Blood samples (n = 10,096) collected onto filter papers were taken randomly from ultrasound-negative people who entered the study, of which 11.2% were found to be seropositive. Seropositivity increased with age (P < 0.0001), with females exhibiting higher seroprevalence than males for all age groups (P < 0.0001). Seroprevalence was distributed occupationally among 17.3% of female students, 11.2% of male students, 8.3% of housewives, 7.3% of farmers, and 6.4% of male civil servants. Housewives and students were more likely to be seropositive (P < 0.0001). Forty-seven percent (526) of the seroreactors kept dogs. All liver hydatid cysts detected by ultrasound during community screening were classified according to morphology and size into six types. Type I (17.5% of all cases) were small univesicular cysts less than 50 mm in diameter with no laminations or daughter cysts. Type II (34%) were univesicular cysts with only laminations. Type IIIa (8.5%) were univesicular cysts with the appearance of laminations and daughter cysts. Type IIIb (13%) were univesicular with laminations and less prominent daughter cysts. Type IV (5.6%) presented as a solid mass. Type V were degenerated calcified or partially calcified cysts (13.2%). Type VI presented as multiple cysts (8% of all cases). The CE cases that exhibited Types II, IIIa, IIIb, IV or VI cysts showed the highest seropositivity (86%, 96%, 95%, 100%, and 96%, respectively), while Types I and V were the least seroreactive (38% and 22%, respectively). Cases of CE occurred in 311 families, with 93% having only one member as a CE case while 7% of the families had two or more cases. However, 25% of the ultrasound-negative persons belonging to families with an index CE case were seropositive for antibodies to Echinococcus. These results confirm the importance of human CE in Libya. They also confirm the usefulness of ultrasound combined with serology as a mass screening approach for CE in north African communities.

Abdomen↗
PubMed1994

Epidemiology and control of parasites in nomadic situations.

Nomadism is a highly specialised mode of life that enables humans to exploit resources that are widely distributed over space and time. The isolation and remoteness of many nomad populations have limited studies on the macroepidemiology of parasitic infection in nomad populations. From the available information, the influence of a number of factors on the prevalence and transmission of parasitic infections in nomads is discussed. Environmental conditions, especially relative humidity and temperature, profoundly influence parasitic diseases. Human behaviour varies with cultural factors and influences exposure to disease. Periodic movements of nomads may either remove them and their animals from contaminated environments or may bring then into contact, often seasonally, with infections. There may be a strong ecological interdependence between diet and infection and disease in nomadic groups. Finally, the influence of drought can be profound in that seasonal or prolonged drought promotes concentration of populations in small areas or their sedenterisation, often with an increase in parasite transmission. Relevant information that needs to be acquired to develop appropriate practical and cost-effective health and veterinary care and control programmes for nomadic populations and their livestock is outlined.

Africa South of the Sahara↗
PubMed1993

The potential of vervet monkeys (Cercopithecus aethiops) and baboons (Papio anubis) as models for the study of the immunology of Echinococcus granulosus infections.

Nine vervet monkeys and nine baboons were infected with eggs of Echinococcus granulosus per os. Six of the vervets and one of the baboons possessed hydatid cysts at autopsy, 15-28 months post-infection. The sequential IgG response to hydatid fluid and protoscolex antigens showed considerable inter-animal variation. Infected vervets and baboons became seropositive after an average of 8 months post-infection. Considerable fluctuation in the IgG response was observed, particularly to the hydatid fluid antigen which, in humans, may contribute to the existence of a significant proportion of seronegative individuals. Vervets, in particular, may be useful to study immunological events associated with exposure, development and resolution of hydatid disease in outbred human populations.

Animals↗
PubMed1992

Prevalence of human hydatid disease in northwestern Libya: a cross-sectional ultrasound study.

A total of 4103 people were screened in an ultrasound survey of the prevalence of hydatid disease (Echinococcus granulosus) in five areas of northwestern Libya; hydatid cysts were seen in 57 (1.4%), an overall prevalence of approximately 2.0% when adjusted for the likelihood of the occurrence of cysts in other sites in the body. All ultrasound-positive cases were confirmed by dot-blot ELISA. The prevalence of hydatid cysts increased with age, and differed between the sexes except in the five to 14 age group. All diagnosed cases, even those with large cysts, were asymptomatic. This study demonstrates the value of ultrasonography for screening field populations for hydatid disease. The technique was well received locally, facilitating the rapid collection of prevalence data from all ages and both sexes. Libyan people keep guard dogs, but there is little direct human:dog contact. Many people own a single dog, invariably kept outside and often chained up. Stray dogs are common, roaming the countryside to scavenge sheep carcases etc., and such dogs could be the main reservoir of E. granulosus in Libya. Because of the minimal direct human:dog contact, transmission of hydatid disease in Libya is probably indirect by ingestion of eggs from contaminated vegetables or drinking water.

Adolescent↗
PubMed1991

Release and survival of Echinococcus eggs in different environments in Turkana, and their possible impact on the incidence of hydatidosis in man and livestock.

In Turkana, Kenya, a prevalence of hydatidosis of nearly 10% has been recorded among the pastoralists yet their livestock have a much lower prevalence of the disease. The present study investigated the release from dogs and subsequent survival of Echinococcus eggs in Turkana huts, water-holes and in the semi-arid environment. The results were compared with the survival of eggs of Taenia hydatigena and T. saginata. The study was repeated under the cooler and moister conditions found in Maasailand where livestock have a greater incidence of hydatid disease than in Turkana but where the incidence in man is ten times lower. The average number of Echinococcus eggs per proglottid is 823. Nine percent of these remain in proglottids 15 minutes after release from a dog and the released eggs lose their viability in less than two, 48 and 300 hours in the sun, huts and water in Turkana respectively: the major influencing factor being temperature. The greater survival of eggs in the houses, coupled with the fact that dogs congregate for most of the day in the small houses facilitating a close man:dog contact, provide ideal conditions for the transmission of the parasite to man. The hostile environmental conditions and lack of contact between dogs and livestock contributes to the lower infection rate in livestock. Conversely in Maasailand, Echinococcus eggs survive in the environment for longer than three weeks and in addition, dogs are used for herding. This partly explains the higher infection rate among Maasai livestock but the low human infection rate remains arcane and requires further study.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1990

Hydatid disease in the Turkana District of Kenya, VII: analysis of the infection pressure between definitive and intermediate hosts of Echinococcus granulosus, 1979-1988.

The rate of acquisition of Echinococcus granulosus and Taenia hydatigena was examined in dogs treated with praziquantel in northwestern Turkana District of Kenya. An attempt was also made to assess the effect of drought on the prevalence of E. granulosus. The infection pressure to dogs with the cestodes was shown to be high, and the prevalence returned to pretreatment levels within six months. The unreliability of arecoline purging in prevalence studies of dog cestodes is shown by mathematical contrast to the results of autopsy. Arecoline purge may underestimate the real prevalence by 10-fold. Dosing intervals in hydatid control programmes utilizing mass dog-purging to estimate re-infection rates should therefore take this factor into consideration. It is proposed that a mass dog-dosing schedule in Turkana, using praziquantel, should take into consideration the short prepatent period of E. granulosus, the financial constraints, and the slaughter practices in the area. During the prolonged droughts which occur approximately every 10 years, the programme will be adjusted accordingly to cater for the initial increase in infection intensity to dogs.

Animals↗
PubMed1989

Observations on the suitability and importance of the domestic intermediate hosts of Echinococcus granulosus in Uttah Pradesh, India.

The present study investigated the suitability and importance of buffaloes, camels, sheep, goats and pigs in maintaining the life-cycle of Echinococcus granulosus in Aligarh, India. A total of 565 (36%) of 1556 buffaloes, 20 (2%) of 1208 goats, 5 (1%) of 559 pigs, 6 (6%) of 109 sheep and two of three camels were found to harbour hydatid cysts. The frequency distribution of the hydatid cysts in each intermediate host species was over-dispersed and in buffaloes cyst fertility increased with increasing cyst size. Of 2171, 95 and four buffalo, goat, and camel cysts examined 327 (15%), two (2%) and three cysts respectively were fertile. No pig or sheep cysts were found to contain protoscoleces. The unfenced buffalo abattoir and the large number of dogs allowed access to the abattoir coupled to the number of buffalo slaughtered in comparison to the other potential hosts, indicates that the buffalo is the most significant host for maintaining the life-cycle of the parasite in this area of India. Applicable control measures for the region are suggested.

Abattoirs↗
PubMed1989

Observations on human echinococcosis (hydatidosis) and evaluation of transmission factors in the Maasai of northern Tanzania.

An attempt was made to estimate the prevalence of hydatid disease amongst the Maasai people of northern Tanzania and to examine the factors which would contribute to the transmission of the disease in this region. Retrospective review of hospital records revealed an annual surgical rate of hydatid disease for 1977 through 1986 of 11 per 100,000 people. Ten (1%) of 959 people screened by ultrasound scanning had hydatid cyst-like echoes, giving a prevalence estimation of 1.4%. Thirty per cent of positive ultrasound cases were also positive in an ELISA antibody test. Three of four dogs necropsied and two of six dogs purged were found to harbour patent Echinococcus infections. Quantitative man:dog contact studies, examination of soil and water samples for Echinococcus eggs and comparison of the anti-Echinococcus antibody responders revealed that there are few marked differences in exposure to infection between the Maasai and the Turkana, who have a much higher prevalence of hydatidosis and perhaps the highest prevalence in the world. Hypotheses to explain the differences in the infection rate between these two groups of pastoralists who share a similar traditional lifestyle are presented. The Maasai, like the Turkana, had no knowledge of hydatid disease, and it is suggested that the best way to control the disease in Maasailand would be by proven dog control measures, supported by a suitable, more durable, educational programme.

Adolescent↗
PubMed1989

Prevalence of human hydatidosis in Uttar Pradesh.

The prevalence of human hydatidosis in eastern U.P. is higher than western U.P. Maximum infection was noticed in liver followed by lungs. The prevalence rate shows considerable variation with respect to sex and age of the patients. Comparison of the present data with previous reports suggests an increasing trend in the prevalence of this disease. Various epidemiological factors responsible for this disease have also been discussed.

Adolescent↗
PubMed1988

Immunodetection of Echinococcus eggs from naturally infected dogs and from environmental contamination sites in settlements in Turkana, Kenya.

A species-specific indirect immunofluorescence test using an anti-Echinococcus oncosphere monoclonal antibody (EgOH6-4E5) was applied to identify Echinococcus oncospheres released from taeniid eggs collected in environmental soil and water samples, and from perianal or faecal samples of naturally infected dogs, in northern Turkana, Kenya. The specificity of immunodetection of Echinococcus eggs by specific fluorescence of Echinococcus oncospheres from naturally infected dogs was 100% when compared to Taenia hydatigena infections, and a sensitivity of 73% was obtained in the detection of dogs infected with Echinococcus using perianal Scotch tape swabs. Taeniid eggs were recovered from various soil samples inside Turkana manyattas (settlements) and from waterhole samples. Some oncospheres obtained from taeniid eggs recovered from all sampled areas, but particularly from inside Turkana huts (akai) and from water samples from open waterholes used by the people and their livestock, reacted positively with the Echinococcus 4E5 monoclonal antibody. The potential importance of contamination of such sites with Echinococcus eggs is discussed in relation to the transmission of echinococcosis in this hyperendemic region of northern Kenya.

Animals↗
PubMed1988

Hydatid disease in the Turkana district of Kenya. VI. Man:dog contact and its role in the transmission and control of hydatidosis amongst the Turkana.

Despite a hostile environment unsuited to parasite transmission, Turkana district in northwestern Kenya has the highest incidence of hydatid disease in the world. The prevalence of the disease varies ten-fold, being higher in the north than the south of the district. This study examined whether differences in man:dog contact and specific activities of dogs enhanced the transmission of Echinococcus granulosus eggs to man. A total of 24,541 observation-minutes were completed, studying 31 dogs from 20 manyattas in six locations throughout Turkana district, and in one location in neighbouring Pokot. Correlations were found between the time a dog spent in a manyatta and whether dogs were allowed to clean children, scavenge from cooking utensils and defecate within the home area. The amount of time a dog spent in a manyatta depended upon the availability of water, food and shade. The study also revealed that it is difficult to change the Turkana's behaviour and attitudes towards their dogs, despite continuous education. Therefore, in an area where home slaughter is practised, dosing of dogs with a suitable taeniacide will for many years to come remain an important component in the hydatid control programme being carried out in Turkana.

Adult↗
PubMed1987

Interspecific characterization of several taeniid cestodes by isoenzyme analysis using isoelectric focusing in agarose.

Taenia cestodes were obtained from 5 different definitive host species in Kenya and 175 different samples were examined by classical morphological methods and by isoenzyme analysis using isoelectric focusing in agarose. Gels were stained for 17 different enzymes and 3 of these were used in the construction of isoenzyme profiles. The samples fell into 25 zymodemes, and no zymodeme contained more than 1 species of Taenia, indicating that isoenzyme analysis can reliably be used for the identification of species of this genus.

Animals↗
PubMed1986

Hydatid disease: research and control in Turkana, IV. The pilot control programme.

A pilot programme to control hydatid disease in north-west Turkana district was started in October 1983 with an intensive educational campaign. This was followed by control and treatment of the dog population to reduce the prevalence of Echinococcus granulosus, thereby reducing the infective pressure on man. Surveillance is by mass annual sero-epidemiological and ultrascan surveys of the nomadic Turkana within the control region and by arecoline purging of the dogs. Some of the recent advances in research on hydatid disease in subject areas such as immunodiagnosis, chemotherapy and epidemiology have been incorporated into the present programme, and their relevance to this and other similar programmes is discussed.

Animals↗
PubMed1986

Experimental infection of the baboon (Papio cynocephalus) with Echinococcus granulosus of camel, cattle, sheep and goat origin from Kenya.

In different areas of the world, strains of Echinococcus granulosus have been described which appear to vary in their infectivity, and laboratory primates have been used as indicators of their infectivity to man. This phenomenon was evaluated in Kenya for hydatid material of human, camel, cattle, sheep and goat origin. Viable eggs, produced by experimental infections in dogs with larval material from all the above intermediate hosts, were fed separately to four baboons (Papio cynocephalus) in each case. Baboons were autopsied between 373 and 501 days following infection and the liver, lungs, heart, spleen and kidneys were thoroughly inspected. Hydatid cysts were recovered from two baboons in each of the camel, sheep and goat groups, three baboons in the cattle group and none of the baboons in the human group. Fertile cysts were found in the cattle and goat groups and it is suggested that the baboon could be used as an experimental model for this parasite.

Animals↗