Post Eclosion Age Predicts the Prevalence of Midgut Trypanosome Infections in Glossina

The teneral phenomenon, as observed in Glossina sp., refers to the increased susceptibility of the fly to trypanosome infection when the first bloodmeal taken is trypanosome-infected. In recent years, the term teneral has gradually become synonymous with unfed, and thus fails to consider the age of the newly emerged fly at the time the first bloodmeal is taken. Furthermore, conflicting evidence exists of the effect of the age of the teneral fly post eclosion when it is given the infected first bloodmeal in determining the infection prevalence. This study demonstrates that it is not the feeding history of the fly but rather the age (hours after eclosion of the fly from the puparium) of the fly when it takes the first (infective) bloodmeal that determines the level of fly susceptibility to trypanosome infection. We examine this phenomenon in male and female flies from two distinct tsetse clades (Glossina morsitans morsitans and Glossina palpalis palpalis) infected with two salivarian trypanosome species, Trypanosoma (Trypanozoon) brucei brucei and Trypanosoma (Nannomonas) congolense using Fisher's exact test to examine differences in infection rates. Teneral tsetse aged less than 24 hours post-eclosion (h.p.e.) are twice as susceptible to trypanosome infection as flies aged 48 h.p.e. This trend is conserved across sex, vector clade and parasite species. The life cycle stage of the parasite fed to the fly (mammalian versus insect form trypanosomes) does not alter this age-related bias in infection. Reducing the numbers of parasites fed to 48 h.p.e., but not to 24 h.p.e. flies, increases teneral refractoriness. The importance of this phenomenon in disease biology in the field as well as the necessity of employing flies of consistent age in laboratory-based infection studies is discussed

Effect of Improved Feeding and Housing, Friesian Blood Level and Parity on Milk Production of Ankole x Friesian Crossbred Cows

In North Kivu, D.R. Congo, cattle are raised in extensive systems based on local breeds and crossbreds. This farming method affects the performance of dairy animals and mortgages the level of milk consumption in population. An improved farming system, including feed supplementation, Friesian cross-breeding and the sheltering of animals in stalls at night, was studied to evaluate its effect on milk production by Ankole x Friesian crossbreds. The study was performed in Beni, D.R. Congo, on two groups of 15 animals (control group-CoG and improved group-IG), homogeneous according to Friesian blood and parity levels. The improved system, Friesian blood and parity levels increased significantly milk production (P<0.001). Farming system increased milk production by 1.6 l/d (5.2 l/d vs 6.8 l/d respectively in CoG and IG). Milk production ranged from 5.3±0.04 l/d to 6.6±0.02 l/d and from 4.9±0.02 l/d to 7.2±0.02 l/d according, respectively, to Friesian blood level and parity. A significant interaction was observed between farming system and Friesian blood level, and between farming system and parity (P<0.001). The two groups were characterized by a fair adaptation to forage availability associated to climatic factors. The study showed the importance of genetic and environmental factors on the milk production of crossbred dairy cows of the region

Identification of hard ticks (Acari: Ixodidae) and seroprevalence to Theileria parva in cattle raised in North Kivu Province, Democratic Republic of Congo

This study aimed to identify tick species and to determine their relationship with the Theileria parva seroprevalence in cattle raised under an extensive farming system in North Kivu Province, Democratic Republic of Congo in two agro-ecological zones namely medium (1,000-1,850 m) and high (>1,850 m) altitude. Among the 3,215 ticks collected on 482 animals, from February to April 2009, Rhipicephalus appendiculatus (64.26 %), the main vector of T. parva, was the most abundant species followed by Rhipicephalus decoloratus (35.49 %) and Amblyomma variegatum (0.25 %). The mean burden of R. appendiculatus tick per infested animal appeared significantly higher at medium (6.5 +/- 0.22 ticks) than at high (0.07 +/- 0.3 ticks) altitude (P 0.05) different between medium (48.4 %; 95 % CI: 38-49) and high (41.9 %; 95 % CI: 35-49) altitude. These relatively low seroprevalences suggest that there is a state of endemicity to T. parva infection in the study area. The presence of the tick vector on animals was associated with an increased risk of being seropositive to T. parva infection (odds ratio = 2.04; 95 % CI: 1.8-2.3; P < 0.001). The results suggest the need for a longitudinal study to investigate the seasonal dynamics of tick species and T. parva infection. The rate of tick infection should also be evaluated in order to determine the intensity of T. parva transmission to cattle

Screening of Trypanosoma brucei gambiense in domestic livestock and tsetse flies from an insular endemic focus (Luba, Equatorial Guinea).

BACKGROUND: Sleeping sickness is spread over 36 Sub-Saharan African countries. In West and Central Africa, the disease is caused by Trypanosoma brucei gambiense, which produces a chronic clinical manifestation. The Luba focus (Bioko Island, Equatorial Guinea) has not reported autochthonous sleeping sickness cases since 1995, but given the complexity of the epidemiological cycle, the elimination of the parasite in the environment is difficult to categorically ensure. METHODOLOGY/PRINCIPAL FINDINGS: The aim of this work is to assess, by a molecular approach (Polymerase Chain Reaction, PCR), the possible permanence of T. b. gambiense in the vector (Glossina spp.) and domestic fauna in order to improve our understanding of the epidemiological situation of the disease in an isolated focus considered to be under control. The results obtained show the absence of the parasite in peridomestic livestock but its presence, although at very low rate, in the vector. On the other hand, interesting entomological data highlight that an elevated concentration of tsetse flies was observed in two out of the ten villages considered to be in the focus. CONCLUSIONS: These findings demonstrate that even in conditions of apparent control, a complete parasite clearance is difficult to achieve. Further investigations must be focused on animal reservoirs which could allow the parasites to persist without leading to human cases. In Luba, where domestic livestock are scarcer than other foci in mainland Equatorial Guinea, the epidemiological significance of wild fauna should be assessed to establish their role in the maintenance of the infection

Identification of different trypanosome species in the mid-guts of tsetse flies of the Malanga (Kimpese) sleeping sickness focus of the Democratic Republic of Congo

<p>Abstract</p> <p>Background</p> <p>The Malanga sleeping sickness focus of the Democratic Republic of Congo has shown an epidemic evolution of disease during the last century. However, following case detection and treatment, the prevalence of the disease decreased considerably. No active survey has been undertaken in this focus for a couple of years. To understand the current epidemiological status of sleeping sickness as well as the animal African trypanosomiasis in the Malanga focus, we undertook the identification of tsetse blood meals as well as different trypanosome species in flies trapped in this focus.</p> <p>Methods</p> <p>Pyramidal traps were use to trap tsetse flies. All flies caught were identified and live flies were dissected and their mid-guts collected. Fly mid-gut was used for the molecular identification of the blood meal source, as well as for the presence of different trypanosome species.</p> <p>Results</p> <p>About 949 <it>Glossina palpalis palpalis</it> were trapped; 296 (31.2%) of which were dissected, 60 (20.3%) blood meals collected and 57 (19.3%) trypanosome infections identified. The infection rates were 13.4%, 5.1%, 3.5% and 0.4% for <it>Trypanosoma congolense</it> savannah type, <it>Trypanosoma brucei</it> s.l., <it>Trypanosoma congolense</it> forest type and <it>Trypanosoma vivax</it>, respectively. Three mixed infections including <it>Trypanosoma brucei</it> s.l. and <it>Trypanosoma congolense</it> savannah type, and one mixed infection of <it>Trypanosoma vivax</it> and <it>Trypanosoma congolense</it> savannah type were identified<it>.</it> Eleven <it>Trypanosoma brucei gambiense</it> infections were identified; indicating an active circulation of this trypanosome subspecies. Of all the identified blood meals, about 58.3% were identified as being taken on pigs, while 33.3% and 8.3% were from man and other mammals, respectively.</p> <p>Conclusion</p> <p>The presence of <it>Trypanosoma brucei</it> in tsetse mid-guts associated with human blood meals is indicative of an active transmission of this parasite between tsetse and man. The considerable number of pig blood meals combined with the circulation of <it>Trypanosoma brucei gambiense</it> in this focus suggests a transmission cycle involving humans and domestic animals and could hamper eradication strategies. The various species of trypanosomes identified in the Malanga sleeping sickness focus indicates the coexistence of animal and human African Trypanosomiasis. The development of new strategies integrating control measures for human and animal trypanosomiasis may enable the reduction of the control costs in this locality.</p