Characterization of Tanzania shorthorn zebu cattle for tolerance to ticks and East Coast Fever
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Date
2017
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Sokoine University of Agriculture
Abstract
In Tanzania, livestock diseases, especially tick bone diseases (TBDs), impose loses to
livestock in terms of mortality, decrease in production and increased costs of control
measures. Among the TBDs, East Coast fever (ECF) is the most prevalent and fatal
disease. The main control measure for TBDs is use of acaricides to control the vector
ticks, chemotherapy of sick animals as well as immunization of cattle by the infection and
treatment method (ITM). The applications of these are control measures are often limited
by high costs of acaricides and veterinary drugs, development of resistance by vector
ticks and the parasites as well as negative environmental impacts. This necessitated the
search for alternative ways to control TBDs with minimum use of acaricides. Indigenous
breeds of cattle are said to be tolerant to TBDs and adapted to harsh conditions prevailing
in rural areas. Among the Tanzania Shorthorn Zebu (TSHZ) cattle, Tarime cattle are
believed by livestock keepers to be tolerant to ticks and ECF. However, there are no
scientific investigations which have been conducted to verify the farmers’ beliefs.
Therefore, studies were conducted to validate the farmers’ belief that Tarime cattle are
tolerant to ECF.
In the first study, a cross-sectional survey was conducted in four selected districts of Mara
(Serengeti and Tarime) and Simiyu (Maswa and Meatu) regions to determine the
perception of livestock farmers on ticks, tick-borne diseases and tolerance of their cattle
to TBDs. In the second study, tick burden and prevalence of Theileria parva (T. parva)
infection in Tarime cattle found in Serengeti and Tarime districts were assessed. In the
third study, an on-station experiment was conducted to compare tick burden and induced
immunity due to T. parva infection in Tarime and Sukuma zebu cattle under different tick
control regimes. The fourth study was a review on tolerance of TSHZ cattle to ticks and
ECF. In the first study, a well structured questionnaire and personal observation were
used to collect information. The aim of the study was to assess farmers’ knowledge and
perceptions on tick species, tick-borne diseases, tick control measures, production
constraints and tolerance of Tarime and Sukuma zebu cattle to TBDs. The study involved
60 agro-pastoralists from each of the districts of Serengeti, Tarime, Maswa and Meatu in
Tanzania, making a total sample size of 240 livestock farmers. Data were collected
through individual interview using a structured questionnaire. The results show that,
livestock diseases were ranked as the first important problem affecting cattle production
in Serengeti and Tarime districts while in Maswa and Meatu districts lack of livestock
feeds during the dry season was ranked as the most important constraint, followed by
livestock diseases. Among the diseases affecting cattle, the TBDs ranked first in Serengeti
and Tarime districts while in Maswa and Meatu districts the TBDs ranked fourth and
sixth, respectively. Most (74%) of the livestock farmers interviewed knew well the signs
of the different TBDs. The majority of the respondents in all districts knew that ECF is
caused by ticks, but did not associate the other TBDs with ticks. Most of the farmers
interviewed were using acaricide to control ticks, and the most common method of
application was hand spraying. All farmers used Oxytetracycline to treat TBDs, however,
some farmers used local herbs. Although most farmers knew the signs of TBDs, they
were not spraying/dipping their animals on regular basis due to economic reasons and the
belief that their animals always carry ticks without being sick or dying and ECF affects
only calves. About half of the farmers considered their breeds to be tolerant to ticks and
ECF. It is concluded that, the livestock farmers in the Lake zone have substantial
knowledge on tick species and TBDs symptoms and they consider ECF as less important
disease compared to the other TBDs.
The second study was carried out to assess the distribution, abundance of different tick
species and the prevalence of T. parva infection in Tarime zebu cattle kept in selected
wards of Serengeti and Tarime districts in Mara region. Adult ticks were sampled,
identified and counted from 360 animals which were extensively managed in communal
rangelands. Concurrently, blood samples were collected and thereafter DNA extracted
and nested polymerase chain reaction (nPCR) carried out to determine the prevalence of
T. parva. Two primers specific for p104 gene were used in PCR amplification to detect
the presence of T. parva DNA. Four genera of ticks, namely, Rhipicephalus, Amblyomma,
Boophilus and Hyalomma were identified. Rhipicephalus spp accounted for 71.8% of the
total ticks whereas Amblyomma, Boophilus and Hyalomma constituted 14.1%, 14.0% and
0.1% of the ticks, respectively. There was significantly (p < 0.05) more animals infested
with ticks in Tarime district (96.1%) than in Serengeti (61.7%). The average counts of
ticks were higher in adult animals (p < 0.05) than in young animals. The overall
prevalence of T. parva was 27.7% and was significantly (p < 0.05) higher in Serengeti
(38.3%) than in Tarime district (16.7%). Interestingly, it was observed that, all animals
which tested positive for T. parva did not show any clinical signs of ECF, suggesting
existence of subclinical infection in Tarime zebu. These results suggest that Tarime cattle
can tolerate ECF infection and are likely to save as potential carriers of T. parva to other
less tolerant cattle breeds in mixed herds. Since Tarime cattle are preferred by most
farmers with mixed herds, routine screening for T. parva is highly recommended to
minimize introduction of infected cattle into an immunologically naive population.
The third study was conducted to determine tick burden and immunological parameters of
resistance to ECF in Tarime and Sukuma zebu strains exposed to natural tick infestation.
Tick load, Packed Cell Volume (PCV), T. parva specific antibody percent positivity (PP)
and prevalence of T. parva parasites were studied in relation to dipping regime, breed,
and season of the year. A total of 25 animals per strain were used in this experiment.
Animals of each strain were divided into three groups. Animals in group I were dipped every two weeks while those in group II were dipped every three weeks. Animals in
group III were not dipped at all. Comparison of effect of dipping frequency on tick
burden showed no significant (p > 0.05) differences when cattle which were dipped in
each strain either once every 2 or 3 weeks in the two seasons. However, Tarime cattle had
significantly higher (p < 0.05) tick count than Sukuma cattle and non dipped groups
maintained high tick infestation throughout the experimental period. The PCV values in
all cattle were within the normal physiological range; although this parameter was
significantly lower (p < 0.05) in Tarime cattle. All cattle regardless of breed were sero
positive (had antibody levels above ELISA cut-off point), but Tarime cattle maintained
higher antibody percent positivity compared to Sukuma cattle by 15%. Conversely, the
prevalence of T. parva parasites was lower in Tarime (36%) compared to Sukuma cattle
(38%), although the difference was not significant. During the study period 20% (5/25) of
Sukuma cattle contracted ECF, but none of the Tarime cattle showed any clinical signs
for the disease. The differences between the two zebu strains shown in terms of antibody
percent positivity and T. parva parasite prevalence indicate different ability of the two
cattle strains to resist tick infestation and ECF infection under natural challenge. Thus, the
higher antibody levels but lower parasite prevalence under high tick challenge observed
in Tarime cattle, suggests a high proportion of individual animals in this strain, which are
carriers of T. parva. Thus, these findings confirm the farmers’ perceptions on suitability
of Tarime cattle under prevailing ecological conditions in the Lake zone of Tanzania.
The fourth study was a review on the prevalence and tolerance of Tanzania Shorthorn
Zebu cattle to East Coast fever in Tanzania. A search of peer-reviewed publications on
ECF, ticks and ECF tolerant cattle in Tanzania was conducted from comprehensive
databases including PubMed, Science Direct, Swetswise and CAB direct. The search was
extended to available theses, conference proceedings and project reports. The findings show that ECF is not seen by most livestock keepers as the most serious disease
compared to other TBDs. This is because the zebu cattle which are predominantly kept all
over the country are thought to be tolerant to ticks and ECF. Some of the zebu strains
which are thought to tolerate ECF are Sukuma, Tarime, Maasai and Fipa cattle. In all agro
ecological zones the most prevalent tick species is R. appendiculatus, this implies that the
TSHZ cattle are at risk of being infected with ECF if the animals are not resistant and
proper tick control regimes are not observed. In Tanzania, ECF control has mainly relied
predominantly on tick control using acaricides and chemotherapy while ECF
immunization has been recently introduced. Some research results also showed that,
immunization can boost immune status of indigenous cattle and, if ECF immunization can
be sustained, large areas are expected to be endemically stable. However, the adoption of
immunization on wider scale is questionable due to its cost and change in farmers’
attitudes, socio-demographic and environmental concerns. The study recommends
interdisciplinary collaboration between veterinary epidemiologists, socio and agricultural
economists and ecologists not only to find a single most suitable method of ticks and ECF
control but to integrate the available methods with tolerant strains of cattle available to
create endemic stability condition for the disease which can reduce the complexity of the
whole process.
Generally, the findings of this study confirm farmers’ perception on the ability of Tarime
cattle to tolerate ECF infection under prevailing ecological conditions in the Lake zone of
Tanzania. The use of this strain, therefore, can be an alternative way of minimizing
acaricide usage, whereby application can be done on monthly basis. However, when
Tarime and other breeds are kept together, screening of the animals for presence of T.
parva parasites is recommended. From these findings it is concluded that using Tarime
cattle could be effective and economical in rural areas as it minimizes the use of synthetic
acaricide to control ticks and TBDs. Further research studies to determine the gene
responsible for tolerance of Tarime cattle to ECF are recommended.
Description
A THESIS SUBMITTED IN FULFILLMENT OF THE REQUIREMENTS FOR
THE DEGREE OF DOCTOR OF PHILOSOPHY OF SOKOINE UNIVERSITY OF
AGRICULTURE. MOROGORO, TANZANIA. 2017
Keywords
Shorthorn zebu cattle, East Coast fever, Tick bone diseases, Livestock diseases, Tanzania